I would formally request (in writing) a Functional Behavior Assessment (FBA) with a resulting Behavior Intervention Plan (BIP) right away. Punishing for behavior related to disability is not acceptable.
Have you called your local Arc office for help in advocating at school? https://www.aogh.org/special-education-advocacy
Try this organization as well: http://www.heartadvocates.com/
Here’s more on the FBA (#5 in this article):
Penny
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism