Welcome.
I'm so sorry your DS and your family are going through this ordeal. Is the therapist knowledgeable about gifted? Is s/he able to schedule an advocacy meeting with you and the school, to advise the school that the behavior may a "symptom", not the "root problem" and that higher academics which respect his intelligence and give him new things to learn as well as intellectual peers to discuss ideas with... may be the Rx? If not, could the therapist recommend someone?
The situation sounds sufficiently detrimental that it may be wise to pull your child from the school. Is kindergarten attendance required in your area? Could he homeschool/unschool/de-school for the remainder of this academic year, while things are sorted out with the school for possible reintroduction at a future point?
Reviewing academic reports from a prior school, sharing a portfolio of his works, a reading list of books he's enjoyed, taking end-of-year tests, seeing the school's end-of-year outcomes and checking off the ones you have observed that he has mastered... are some of the ways parents have opened a discussion for acceleration.
The Iowa Acceleration Scale (
IAS) is the gold-standard for acceleration and you may wish to open a discussion on that with the school.
A few ideas on successful advocacy
here.
Wishing you all the best with this - trust your mom intuition - you know your child best.
