It’s easy to think you know the prerequisites when in fact you don’t.

For instance, a student struggling in calculus may think they know algebra because they got a decent grade in algebra class, even though they struggle to solve a quadratic equation and they’ve forgotten how trig works.

– Maybe they got saved by grade inflation.

– Maybe they did learn these things but they’ve gotten so rusty that they need to effectively re-learn them again.

– Maybe they learned and still remember everything from their algebra class, but the class was watered-down and cherry-picked the simplest possible cases of problems within each topic (e.g., quadratic equation always has leading coefficient of 1 and is solvable via factoring).

There’s a million different ways that a student can look at a list of prerequisites and mistakenly think that they have learned them.