regularly let him talk about his interaction with teachers. teachers he love. teachers he hate but respect. teachers who are disrespectful. biggest mistake my parents made was assuming that, every time I had a disagreement with an adult, i must be in the wrong by default. so younger me stopped talking about problems. and adult me stopped talking to them. he should keep talking to multiple teachers. if the number of teachers he can talk to somehow becomes smaller and smaller and become one or two over time, that is not a good sign. people who are not tracking the number will assume it's a Good Will Hunting situation where two very "above and beyond" educators are saving a very different student. but that can't be what's going on. It's either him losing confidence because of something, or two teachers intentionally isolating him. if it's former, find out why. if it's latter, it's time to get them fired.