Literature and ancient history. My assessments are almost nothing but essays and long answer. We always lose marks for not responding correctly to the question or not wording our essay clearly enough, rather than not knowing the course content. But we never actually learned how to write an essay to the desired standard. I've been given better resources for learning how to write an essay in psychology than I have in the other two, and we've done only one psych essay over the course of the entire year.

I'm complaining over classes I don't intend to keep, much less care about, but it still feels weirdly frustrating. Did anyone else get this idea when they were at school?

My English classes were always excellent for teaching us how to write essays, as was History. Conversely to you, it was Psych that completely failed to educate us on what they were looking for in an essay. I ended up writing mine like an English/History essay for my first one and got marked down for incorrect structure.

Just go to the teachers and ask them to show you an example high-marks essay. Once they produce that, just use the same structure. If they criticise you on it, you can point to the example and say "point out the differences between my structure and the example essay." Boom.

Purdue OWL is your friend when it comes to essay writing.