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:
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.