I'm being asked about a school code.

When completing your state return, many times there may be a school tax associated with the school district you live or previous lived in if you were a part year resident.  Or the state may just be tracking tax and income amounts from residents in each school district.  In TurboTax, there should be a drop down of school districts and codes associated with those school districts.  Choose your school district you lived in on 12/31/2020 or lived in prior to moving out of state.  If you are unsure of the code, go to your State Department of Revenue website for more information on school district codes.