At my high school, I cannot recall hearing a conservative opinion expressed by a teacher, despite the fact that I lived in a conservative swath of north San Diego county. My teachers were almost entirely Democrats, and were vocal about their beliefs.
I was told by my Chemistry teacher that a single-payer healthcare was the only “fair” system. I had a World History teacher tell us that the natural and best way for society to progress was to turn to communism. Not Cuban Communism, or Soviet Communism, but “true Communism,” because the Soviets just didn’t implement it correctly, we were taught. I even had an English teacher who forced us to spend three months analyzing writing through a Marxist lens, because apparently we “have spent our whole lives hearing about capitalism.”