For me, it was mainly the philosophy and politics teachers. Boy oh fucking boy, for some reason, every single one of my philosopy and PolSci teachers were... interesting personalities to say the least. It was our philosophy teacher who introduced us to the Labor Theory of Value, oddly enough, and the issue of economic inequality. And as for the PolSci-Side, two teachers stand out: One grew up in the GDR and was very, very nostalgic about it (with some fair criticisms, especially concerning the Stasi), and the second, and final one in my case, was an irony-poisoned super-leftist with a gigantic disdain for the rich, the state and capitalism.
The art teacher at the private boys high school I got a scholarship to was always very understanding. She didn't enforce any of the racist hair rules or uniform rules, and openly supported and encouraged the only openly gay student in a school of thousands, which as a closeted bi person, made me feel safe in a school of homophobes. I still remember when she kicked out a student for using the f_____t slur from her class. She also openly talked about politics and protesting the government. Eventually she got bullied out of teaching us by the stockholm syndrome boys because they wanted a traditional male strict figure. And by bullied, I mean literally cyber bullied by almost a whole class. The school moved her to teach the more junior grades, and I still feel incredibly sad about the whole situation.