What state are you in?
School district income tax (SDIT) withholding should be shown in box 19 of your W-2, with the SD number or name inbox 20 and the amount of wages subject to SDIT in box 18.
Ideally, you get a corrected W-2 form your employer. Lacking that, you'll need to use a workaround. Depending on the state, you may be offered a chance in the interview to enter it,