There is so much to take in that we divide up our task subject by subject, rarely allowing something we’ve learned in one class (or other environment) to leak over into another. This is not, in general, a good thing.
Scientists try to ask simple questions and to design a controlled experiment, with “all other things being equal.” It’s rarely possible.
As we progress in school, the lessons get more difficult and complicated. Sometimes they’re difficult because we have to unlearn things.
High School chemistry rests on a base of sophisticated quantum mechanics. Fortunately, it’s not necessary to master the advanced subject in order to use its results.