Gen-X here. The main thing they talked about was how communism was bad because it stifled creativity and freedom, and became a system of simply trying to cover your ass and not get shot.
But this was also separate from dictatorships, which are also bad and we talked about both, especially those in current events, such as in africa. When putting both communism and dictatorships together, it's doubly bad. But for some reason, communism is always accompanied by despotism and nepotism, probably because it's really, really easy to be a dictator in such systems and put your corrupt friends and family into high places, and getting there with communistic promises to the people.
In these high-school discussions, they also talked about McCarthyism, blacklists, gulags, serbia, "disappearing", witch hunts, nuclear proliferation, Cuba, and how governments are assholes regarding communism, including ours. I also had a good history teacher, and even people that didn't want to be there got something out of it. Granted this was American History and during the cold war, so we concentrated on how the americans reacted to the threat of communism, including the wars, "domino theory", house unamerican activities, etc., and what was currently happening in politics and current affairs such as the massive war industry we were building up (which I worked for decades later).
You also have to remember Vietnam war was still fresh in our minds, and everyone knew some older veterans at the time. We talked about socialism and the differences, but they were generally mistakenly equated just as they are today, such as conflating kleptocracies like Venezuela to socialism to communism to left-wing. You see that bullshit a lot from today's right-wing.