Brief Update: met with the teacher yesterday. She says DS is constantly disrupting the class and she does not know how to respond/handle his behavior. She tried to have a student sit with him and calm him down, and then they sent him to another teacher to calm down. It was the most awkward meeting ever. I asked what was her professional opinion and she says she has never dealt with a child with outbursts before. I asked if she thought he was a good fit for her class and the school and she says she didn't know because of his outbursts but he seemed very intelligent from the conversations she has been able to have with him. I asked if she thinks he is on the first grade level, and she just said that the curriculum they are using is "very advanced."
We will be touring another school next week. In an ideal world, I would happily homeschool at this point but I worry about starting such a big undertaking at 6 months pregnant.
I'm not sure if anyone else has said this: it sounds to me like you need a professional evaluation (neuropsychologist or developmental pediatrician). If you go the regular psych eval route, you'll likely end up with a very descriptive report that describes things you already know.
You can also request an educational evaluation through the public schools, even though he's enrolled in private, at least in my state.
"Outbursts" of this magnitude are unlikely to be directly related to a poor curricular fit, I think. If he were under or over challenged academically, I think you'd see behaviors, but not to this degree.
I wouldn't put too much stock in the "advanced curriculum" comment. The teacher probably doesn't understand what's going on any better than you do.
edit: Call the public school DS would be enrolled in and ask how to make a request for educational evaluation, they should be able to route you. Also/or: ask pediatrician for referral for neuro/developmental eval--they should be familiar with people who can do these evaluations and how the referral process works.
Public school option is free to you but more difficult to access (and might miss things a medical professional wouldn't).
