I have posted on here before, that my DS (6 years old at that time) got a "time out" in 1st grade because he interrupted a math class to dispute the teacher's statement that a triangle could have all 3 angles to be 90 degrees simultaneously. He said that he politely stated that 90+90+90 would be greater than 180 degrees and hence she was wrong. He is also the type of person who does not back down and keeps repeating his point of view if he knows that he is right. I can imagine how it looked for the teacher. But, in her place, I would have apologized to the kids and corrected myself and moved on. Not, given a 6 year old a timeout and a bad remark on his weekly "comportment report" for the incident. As an adult, it is perfectly normal to forget things that we learned in elementary school if we never put them to use or revisited them in our later life. That was the lesson that I taught DS from that incident. BTW/ that was the only ever timeout that he got (the teacher lost her job, due to other parents complaining about other issues with their kids).
