His teacher says he's very sweet and listens well. She said she doesn't think she's ever yelled at him. She says he seems nervous to talk to her though. So far I've spoken to his teacher and the school psychologist and they've only suggested doing things that we're already doing so I may have to contact them again.
A teacher who doesn't yell will be certain that no yelling occurred. Not acceptable. I would keep a dated log based on comments from your DS going forward regarding the yelling and address the issue of inappropriate classroom management with the principal after having a pointed conversation about the yelling with the teacher.
On the nervousness around the teacher, that could easily be a by-product of an aggressive/yelling teacher or an inappropriate educational fit. On the latter, if your DS is being required to assimilate to a level below his own, he's effectively being required to engage executive function well above age level. Maintaining a mask is tiring and, understandably, could induce some anxiety in the classroom setting.
My answer obviously doesn't touch on the core issue of academic fit, which is also likely at play.
Another potential source of anxiety for your DS could be coming from the teacher actively suppressing him to get the other students engaged, because he's already reading and they're doing letters still.
Same for my DS in kindergarten. He was only registered for half-days to minimize his exposure (as homeschooling wasn't then an option). In a large class with multiple achievement levels, there is a very real phenomenon of silencing the most capable to encourage general participation.
