When my kids were in public school. We bought a home in a pretty conservative school district at the time.
Very few times did I have to intervene.
When I saw something I did not agree with, I sat my boys down and explained what I thought.
As a parent I never abdicated my responsibility as the last word in my children's education, so good for you for checking up on this stuff.
My kids knew that just because a teacher said something did not make it true. Facts vs opinions.
I also warned them that they will never change a liberal teachers mind about stuff and it was just important to do what you needed to pass the class and graduate.