Tracking science kits, programs, and curriculum that are shallow by design (or default) - and those that go deep.
The Science Ed Ledger tracks K–8 science curricula across several publishers. What they teach, how they teach it, whether the foundational science holds up. We score every unit on the What-Why Gap, Mapping Errors, and Factual Errors. Updated as we evaluate new programs.
Every science curriculum hands students a mental map of how the world works. We found three problems that can make that map unreliable and most curriculum reviews don't measure any of them.
Imagine someone gives you a map with a destination marked but no "You Are Here." You can see where you're supposed to go, but you have no idea where you're starting from. You'd have to guess and every direction you walk would be based on that guess.
That's what happens when a science curriculum asks a child to explain why ice melts, why magnets attract, or why batteries die without first teaching that everything is made of atoms, molecules, electrons or photons. The child doesn't sit there stumped. They build an explanation anyway, from whatever makes intuitive sense. Heat is a substance that "flows in." Cold is a thing that "gets in." Energy is a fluid that "gets used up." These invented explanations feel reasonable. They're also wrong and they become the misconceptions students carry into middle school, high school, and beyond.
The What-Why Gap measures the distance between when a curriculum asks students to explain a phenomena, and when it gives them the actual causal actors - atoms, molecules, electrons - that would make a real explanation possible. A wide gap means students are navigating without a starting point.
Now imagine your map does have a "You Are Here," but the street signs are from a different era. The hospital is labeled "House of Humors." The power plant is labeled "Fire Spirit Temple." You can find the buildings, but every label tells you a story about what's inside that will actively prevent you from understanding what's actually happening there. You won't know that modern medicine is found at the House of Humors or that you can pay your electric bill at the Fire Spirit Temple.
That's what happens when a curriculum uses language like "heat flows into the cold object" or "energy is used up" or "force is stored in the spring." These aren't random mistakes but pre-atomic misconceptions. They describe the world the way people understood it before we knew about atoms. "Heat flows" treats heat as a substance that travels from place to place. In reality, there is no substance called "heat"; there are molecules moving faster and colliding with molecules moving slower. The curriculum is labeling a modern city with medieval cartography.
Mapping Errors measure how often a curriculum's explanatory language points students toward ideas science left behind. Every wrong label becomes a mental model the student must later un-learn and because un-learning is harder than learning, many never succeed.
Some problems aren't about framing or sequence, they're about getting the science wrong. A factual error is a statement that contradicts established science. Not ontologically imprecise language, not a defensible simplification - just wrong. "Conversions between energy and matter do not occur." "Electrons don't move in a wire." "Mass and weight are the same thing." – these are all wrong.
Factual errors are a disqualifier. A curriculum that teaches something scientifically false cannot be recommended regardless of how well it scores on other dimensions. Any unit with a confirmed factual error receives a Not Recommended verdict.
The first problem creates a gap where students need to explain an observation or phenomenon but don't have the players. The second problem fills that gap with category errors and the language installs wrong mental models where correct ones should be. The third is the floor falling out - the science itself is wrong. Together, they build a mental model of how the world works that actively works against students when the real science arrives in later grades.
The students who struggle in high school chemistry and physics aren't struggling because science is hard. Many of them are struggling because they have to un-learn what their early curriculum taught them before they can learn what's actually true. That un-learning is the hidden cost of a shallow curriculum - and it's what the Science Ed Ledger measures.
You can see these problems yourself in about 60 seconds:
"However, in the end, I think that, just as we cannot understand many properties of matter without atomic and sub-atomic understanding, we cannot clearly understand many of the commonly used terms for forms of energy until we break them down again into the underlying particles and their interactions." Helen R. Quinn, Teaching and Learning of Energy in K–12 Education, p. 17
The Science Ed Ledger scores K–8 science programs on one specific thing: whether they connect what students are asked to explain to the atoms, molecules, electrons, and photons that actually do the explaining. That is the lens. It is not a general rating of program quality, and it does not claim to be neutral about depth. It is openly committed to the idea that causal grounding is what makes early science hold up later.
The instrument was not originally built to grade other people's programs. I built it to audit my own. I am Rebecca Woodbury, the author of Real Science-4-Kids (RS4K), an atoms-first K–8 curriculum, and I needed to find where my own books drifted. Where a concept got named but never grounded. Where the language slipped into treating energy or heat as a substance that flows. Where a fact had gone stale, which happened most in astronomy, because the numbers keep changing. The instrument was built to catch those things in my own work first.
The word "shallow" came from a customer describing what was missing in the programs they had already tried. Once the instrument worked on my books, the obvious question was whether it would say anything useful about anyone else's. So we are using the exact same pipeline, with nothing changed, to separate programs that are shallow (lack mechanistic explanations) from those that are not. We are also looking at the curricular design to see whether the shallow design is intentional (stated in the materials as a design choice) or by default (this is what everyone does so we do it too).
Because I am the person who built the scoring instrument and also wrote one of the programs it scores, there is a real conflict of interest. RS4K passes, and it is not the only program that does. Programs from other publishers pass too, and units within programs that score poorly overall sometimes have strong individual results. The instrument exists to give parents and educators a way to evaluate the programs on the market and make an informed choice based on what is actually in them. RS4K sits on this Ledger and runs through the same pipeline as every other program, with no separate track.
If NGSS alignment is a priority, we have noted each publisher's stated alignment and EdReports can provide full detail. If practices are the priority, we have scored those. If you want something deeper, something that takes a student from basic exposure to fundamental understanding of science concepts, we have provided the metric to evaluate where programs differ and how they rank.
One more thing is worth saying plainly. Every program on this Ledger, including the ones that score well, markets itself as effective. What none of them has done is subject its instructional sequence to an empirical test that could show it does not work. That includes RS4K, so far. The difference is that we are building that test. We are developing a research study designed to measure whether atoms-first instruction actually reduces the misconceptions our instrument identifies, or whether it does not. The study could confirm the thesis behind this curriculum, or it could disprove it. We do not know the answer yet. That is the point.
Building a scoring instrument is one kind of accountability. Subjecting your own program to a study that could prove you wrong is another. We chose both.
We are not asking you to trust that we are independent. We are asking you to check.
The method is public. Every score is built from the same steps, and those steps are written out in full, including the exact formula, on the Methodology page. Nothing about how a score is reached is hidden.
Everyone runs through the same pipeline. There is no gentler path for any publisher, including the one I wrote. The same passages get extracted, the same errors get counted, the same thresholds decide the verdict.
You can challenge any score. If you think a result is wrong, we will show you a sample of the underlying passage data, and anyone is welcome to run the same analysis and dispute what we found.
This is one instrument, measuring one property, run by people who are open about who they are. It is not a consensus body and it is not the last word. The longer-term hope is that evaluation like this expands, with more than one set of hands on it. That does not exist yet, and we are not going to pretend it does. Until it does, the honest description is the one above: a transparent tool, applied evenly, with its own author's program in the dataset and open to challenge.
The full scoring method, including every error type and how the Foundation Score is calculated, is on the Methodology page.
How we evaluate, score, and classify every curriculum on the Science Ed Ledger.
We read the curriculum - the student text, the labs, the teacher guides, the assessments - and extract every passage where a core science concept is taught. That includes passages about matter, atoms, chemical reactions, properties of materials, phase changes, energy, heat, sound, light, electricity, magnetism, cells, photosynthesis, rocks and minerals, stars, and other topics where the correct explanation involves atoms, molecules, electrons, or photons. We also extract observational passages (taxonomy, life cycles, anatomy, earth layers) to check for mapping errors and to assess subject-level anchoring. Every extracted passage is classified, the science is verified, and scores are computed. Sample data from our tables are available upon request. Our methodology is public. If you disagree with a score, the data is there to check.
Science curricula contain many different kinds of passages. Some make causal claims that require atomic-molecular grounding ("heat makes ice melt," "energy is stored in the battery"). Others describe and classify at the observation level ("frogs are amphibians," "the Earth has layers"). Our pipeline distinguishes between these because it would be unfair to penalize a K-1 lesson on animal classification for not mentioning atoms - that lesson doesn't need atoms to be correct.
Every passage is tagged as one of three types:
Observational passages can still contain mapping errors - a geology passage that says "heat makes the rock expand" is observational geology with a substance-model error. Every passage gets checked for mapping errors regardless of type. The passage type only affects the gap score.
For every mechanism passage, we ask: does this passage connect the concept to atoms, molecules, electrons, or photons? If the answer is no - if the curriculum asks students to explain why ice melts, why batteries die, why rocks are hard, why stars shine, without providing the atomic-level agents that would make a real explanation possible - that passage has a gap.
The gap score is the percentage of mechanism passages that lack atomic-molecular grounding. A 0% gap means every mechanism passage is grounded. A 100% gap means atoms are never introduced before explanations are expected. Observational passages are excluded from this calculation - they don't inflate the denominator.
We also check for scaffolding: if a passage doesn't name atoms in that specific sentence, but the same lesson establishes atomic grounding for the same concept elsewhere, we tag it as scaffolded and exclude it from the adjusted gap. The adjusted gap is the primary score - it measures what students actually experience, not whether every sentence repeats the word "atoms."
We check every science explanation for correct ontological categorization - is each concept placed in the right category? In science, some things are entities (atoms, molecules, electrons - things that exist and act), some things are processes (collisions, vibrations, rearrangements - things that entities do), and some things are emergent properties (heat, energy, force, sound, color - measurable outcomes that arise from what entities do). When a curriculum puts a concept in the wrong category, students build a mental model that is structurally wrong - not just imprecise, but categorically misaligned with how the science actually works.
For example: Is energy treated as a substance that can be stored and used up (entity), or as a measurable property that changes when atoms and molecules rearrange (emergent property)? Is force treated as something an object "has" (entity), or as the result of an interaction between objects (process)? Is heat treated as a fluid that flows from hot to cold (entity), or as the transfer of kinetic energy when faster-moving molecules collide with slower-moving molecules (process)?
These misplacements - what we call "mapping errors" - are not minor wording issues. Decades of research in science education has shown that when students categorize a process or emergent property as if it were a substance, the resulting misconceptions are uniquely resistant to correction. Chi, Slotta, and de Leeuw (1994) proposed that many of the most robust student misconceptions arise from placing concepts in the wrong ontological category - treating processes as things - and that correcting these misconceptions requires not just new information but an ontological category shift. Reiner, Slotta, Chi, and Resnick (2000) documented that students consistently reason about heat, light, and electric current as if they were material substances, and that this "substance-based commitment" persists even after direct instruction. Chi (2005) showed that misconceptions rooted in ontological miscategorization are more resistant to change than other types because the student's entire mental framework treats the concept as the wrong kind of thing - adding correct information to the wrong framework doesn't fix the framework.
This is why mapping errors matter more than they appear to. A curriculum that says "heat flows into the ice" is not just using informal language - it is placing heat in the substance category, and every student who reads that sentence adds one more piece of evidence to their mental model that heat is a stuff that moves around. That model will resist correction in high school physics because the student isn't holding a wrong fact - they're holding a wrong category.
We flag three types of mapping error:
The map error score is the percentage of student-facing passages containing at least one mapping error.
References: Chi, M. T. H., Slotta, J. D., & de Leeuw, N. (1994). From things to processes: A theory of conceptual change for learning science concepts. Learning and Instruction, 4(1), 27–43. · Reiner, M., Slotta, J. D., Chi, M. T. H., & Resnick, L. B. (2000). Naive physics reasoning: A commitment to substance-based conceptions. Cognition and Instruction, 18(1), 1–34. · Chi, M. T. H. (2005). Commonsense conceptions of emergent processes: Why some misconceptions are robust. Journal of the Learning Sciences, 14(2), 161–199. · Slotta, J. D., & Chi, M. T. H. (2006). Helping students understand challenging topics in science through ontology training. Cognition and Instruction, 24(2), 261–289.
Separately from framing, we verify whether the science itself is correct. A factual error is a statement that contradicts established science - not imprecise framing, but wrong. "T. rex evolved 170 million years ago" (it lived 68-66 mya). "Human cells have 3 billion base pairs on 46 chromosomes" (actually 6 billion on 46). An unbalanced chemical equation presented as balanced.
Factual errors are a disqualifier. Any curriculum with one or more confirmed factual errors receives an automatic ✕ Not Recommended verdict regardless of all other scores. A mapping error can be compensated for by a good teacher. A factual error teaches students something that is wrong.
We assess whether students engage in genuine scientific practices. Each practice is scored as Present, Partial, or Absent. The practices score is reported but does not affect the verdict. A program with excellent practices and wrong science still gets Not Recommended.
We evaluate seven practices adapted from the NGSS Science and Engineering Practices:
| 1. Asking Questions | Do students ask or respond to investigable questions that drive the lesson - not just answer teacher prompts? |
| 2. Developing and Using Models | Do students build, use, or evaluate models (physical, visual, or conceptual) to explain phenomena - not just look at illustrations? |
| 3. Planning and Carrying Out Investigations | Do students help design investigations with controlled variables, or only follow pre-written procedures? |
| 4. Analyzing and Interpreting Data | Do students organize observations, identify patterns, or draw conclusions from data they collected? |
| 5. Using Mathematics | Do students measure, count, calculate, or use quantitative reasoning - not just qualitative description? |
| 6. Constructing Explanations | Do students construct their own explanations of how or why something happens, grounded in evidence and mechanism? |
| 7. Engaging in Argument from Evidence | Do students debate competing explanations, evaluate claims against evidence, or defend their reasoning? |
Each practice scored Present earns full credit (14.3%), Partial earns half credit (7.1%), and Absent earns zero. The total practices percentage and a color tier (green ≥ 70%, amber 40–69%, red < 40%) are reported on each detail card.
Beyond the passage-level scoring, we check whether each subject area in the curriculum establishes at least one explicit connection to atoms and molecules. A biology unit that says "living things are made of atoms and molecules arranged into cells" is anchored - even if most of its passages are observational. A biology unit that teaches accurate descriptive biology with zero mention of atoms anywhere is unanchored - the "clean but empty" pattern.
Anchored subjects get credit for connecting to the atomic foundation. Unanchored subjects flag a structural disconnect - students learn accurate facts that float free of the explanatory framework they'll need later.
The Foundation Score starts at 100 and deducts for problems found:
Each percentage point of gap costs 1 point. A curriculum with a 12% adjusted gap loses 12 points. The gap captures the proportion of mechanism passages where atomic grounding is missing - the wider the gap, the more the student is navigating without a starting point.
Each mapping error costs 3 points. A curriculum with 9 mapping errors loses 27 points. Map errors are weighted more heavily because they don't just fail to teach the right thing - they actively install wrong mental models. Research shows these ontological miscategorizations are uniquely resistant to later correction (Chi, 2005).
Any confirmed factual error = Not Recommended. FSE overrides the foundation score entirely. A curriculum that teaches wrong science cannot be recommended regardless of what else it gets right.
The formula: Foundation = 100 − gap% − (map error count × 3), capped at 0.
Every scored curriculum receives a depth classification on its detail page. The classification explains why the curriculum scores the way it does - not just what we found, but what produced it.
Colors used throughout the Science Ed Ledger:
Many of the programs we evaluate are aligned to the Next Generation Science Standards. NGSS alignment and foundation depth are independent dimensions. A program can be fully NGSS-aligned and still score Shallow if it delays atomic-molecular theory beyond the point where students are asked to explain phenomena. NGSS alignment tells you the curriculum covers the right topics. Our scoring tells you whether the foundational science underneath those topics is right. They measure different things.
Sample data from our tables are available upon request. Our methodology is public. If you disagree with a score, the data is there to check.
Have a curriculum, kit, or program you'd like us to review? Drop us a note, tell us what you want to see, we'll test it and post the results.