What you said was true. You have to talk to them and find out what they're being taught, then present "truth" in place of false info.
We homeschooled, but did the dual credit route once our son was in the 10th grade. So although he never went to high school, he went full time to community college starting when he was 15.
I do think that most of his profs at the CC were pretty fair and balanced. Even if they were "liberal"...they encouraged student debate. His Government prof was ex-military and a hard core Republican...so he riled up the liberal students.
But still we talked about what he was learning and actually we were glad he was home during those first "college courses" because we could "deprogram" any of the false info he was getting.
My boys go to public school and I have been fine with it. I will tell you most of the teachers live right here in the community and send their children there as well. We have a small community that is very conservative, alot of parental involvement in the schools etc., so our schools reflect our values. My boys tell me stories about their teachers that I think are hysterical, a liberal would have a stroke. One of my son's teachers recently used an example in vocabulary and said "you would never use liberal and intelligent in the same sentance." The kids thought it was funny.