In Math, you take Calculus. It's four semesters. Then you take Real Analysis which is the exact same material all over again, but you actually learn it and prove the theorems instead of just memorizing a few formulas and blindly applying them.

It's the same in Economics where you take Micro and Macro and then junior or senior year you do the same all over again but this time you take it seriously with logical reasoning instead of just memorizing a couple stock phrase explanations.

SICP wants to be both. It's a great book so maybe it can do both. But it's hard for a class to do both.