People can look up a school district's income tax number on the website for their state's department of taxation. Although it varies by state, the state website may allow the user to find the tax number using their ZIP code or address, or it may let users browse by county.
Voters in a school district have a say in the school district income tax, and they have to approve all changes. The tax may be taken out of paychecks, paid on the annual tax return or paid each quarter by the taxpayer. The tax base used can vary. For example, Ohio charges school income tax on the same amount of income it does for state income tax, although there's an alternate base available.