English class is just a place to go to be wrong according to someone with no actual skills.

English itself is the result of numerous rounds of multilingual people mashing together the most efficient bits of other languages. The rules are so inconsistent that there kind of aren't any. Also, written English and spoken English are two different languages with different rules, which is why you sound pompous when reading aloud formal essays and why you have to invent emoticons and even start to do rich formatting and change fonts to translate casual conversation into writing.

Take a persuasive writing class at an American college, typically numbered as ENG-112, they might touch on a few points about how to create effective arguments, they're mostly going to grade on pedantic points of grammar, punctuation, spelling and MLA formatting. They're not going to teach you a damn thing about teaching, partially because they're obligated to generate test scores and testing a skill-based curriculum is more difficult than a pedantic rule following one, and mostly because they don't have any actual teaching skills themselves.

Which is why there is a nationwide industry of your high school teacher teaching you how to use semicolons and a college professor marking you wrong for doing it that way.