You’re probably younger than I am, since you have kids in high school, but this was NOT always the case.
I have kids younger than high school age too.
When I was a college student and grad student, this type of behavior wasn’t common (one did not behave the way Cho did to profs without being thrown out of the class and eventually out of the school). At least not at the Universities I attended.
But, students slanting their writings, be it tests or term papers or essays, in order to not get a lesser grade because they didn’t side with the prof’s viewpoint on a issue, was common. I learned it early on in college.
As for what’s been happening in high school classrooms today, I know because I was high school teacher and some of my students complained all the time about certain teachers and how if one didn’t agree with a teacher’s viewpoint, the paper was graded differently or they received a lesser grade, whatever. And two of my high school age kids have been through this already. One had to write an essay on homosexuality in a book the class was reading. She didn’t see any homosexuality, and neither did I when I read it in high school or when I refreshed my memory by reading it again a month ago. But, the teacher assigned her the homosexual aspect and she had to find passages and research that supported the homosexual inferences. It was really hard to find since there wasn’t many. But it was the side she was assigned to support and write about - which is why I told her that sometimes she’s going to have to slant her writings to what the teacher wants. Obviously, the teacher thought there was a homosexual side. So, we searched, found two articles on it, and that’s what she wrote about even though it wasn’t what she “got” from the book.