get yourself a 504 with the school, get a pair of noise canceling headphones, some fidgets that target your favorite ways to stim, for example a chew necklace, essential oils and a tangle. the chew necklace for oral stimming, the oils for a stimulating smell and the tangle for a quiet fidget to use during class.

I would recommend headphones, fidget toys (if they’re allowed), and some comfort items (it could be like a rock or anything that calms you). Also if your school allows this or has accommodations, I’d recommend recording your classes just in case you do get overstimulated and can’t concentrate or have to step outside

Try to bring fidget toys if you can and have items that help you feel better like headphones or clothes that feel comfortable. Also look into accomodations that can help you feel better such as leaving the class if you get too much stimulation.