Where do I enter expenses for materials I purchased for use while teaching?
Expenses you incurred to purchase educational items as an education professional, and working in primary and secondary schools are entered on screen 4, line 10 (line 23 in Drake18 and prior).This amount is limited to $250 each for the taxpayer and spouse.
IR-2021-28 announced that "Eligible educators can deduct unreimbursed expenses for COVID-19 protective items to stop the spread of COVID-19 in the classroom." See Rev. Proc. 2021-15 for details. The total amount is still limited to a total of $250 per taxpayer.
There are some qualifications and restrictions. See Topic 458 - Educator Expense Deduction.