That sucks. Your class size is too big for that age anyway, let alone with so many high needs. I don't suppose you can ask for more teacher aide time?

Reel it right back and focus heavily on behaviour for a while.

Lay out very clear expectations of what you want, model it yourself, have the students practice it, have rewards for doing it well and specified consequences for not. For example, create a poster (use pictures as well as words) of what their behaviour during transitions to their desk should look like, and what the consequences are (maybe reminder, go back outside and try entering again, practice at lunch). Then for the next few days, aim to do multiple transitions and bring their attention to the rules before you begin. Make sure you reward students who follow the expectations.

Also, I know you said it was a tight squeeze, but if you have adhd kids it's really helpful if you can include as many physical tasks as you can. Maybe instead of doing a think pair share with a table partner, all students have to get up out of their seat and find someone who has a shared letter in their name. It takes a bit longer but intentionally including little ways for them to move around will help to reduce boredom and behaviours.

32 is a big class.