What is the Educator Expenses Deduction?

If you’re an eligible educator according to the IRS, the educator expense deduction allows you up to $250 ($500 if you’re both eligible and married filing jointly and both spouses are eligible educators, but not more than $250 each) of any unreimbursed qualified expenses,

Qualified expenses are amounts you paid or incurred for participation in professional development courses, books, supplies, computer equipment (including related software and services), other equipment, and supplementary materials that you use in the classroom. For courses in health or physical education, the expenses for supplies must be for athletic supplies.

This deduction will appear on the Educator Expenses line of your federal tax return. 

See IRS Publication: Topic No. 458 Educator Expense Deduction
Or IRS Publication 529, Miscellaneous Deductions (search for “Educator expenses”)