Great ideas listed so far.

Some additional ideas:

Can you have a bottle of water with you? Maybe try a sports bottle, or if you like herbal tea, have a thermos with you. The act of shifting your attention, drinking, and linking this with a soothing word or phrase could help.

If you are able to have a notebook open to take notes during class, have a section where you can also as needed write something soothing and calming to yourself.

Sarah