Can I take away a school district if I only have one on my W-2?

It sounds as if there is a 2nd entry for the school district on your W-2?  If it will not let you delete that entry, you may want to delete the whole Form W-2 and re-enter with just one entry. 

You can still file an extension today with an estimate of your taxes based on the information you have already entered. That will give you until October 15th, 2022 to file the full return.  If you will owe taxes, you will want to pay an estimate of that now, so you will only on interest on any extra amount. If you pay too much, it will be refunded to you.  Please click here for a TurboTax Help article with information about  TurboTax Easy Extension found at the bottom of the left menu bar.  TurboTax Easy Extension