I am on the school district page, I accidently put the same school district twice. How do I delete one?

Use the "Delete a Form" tool to remove the extra school district tax form (SD 100?) from your state return.

See: How do I delete forms in TurboTax Online?

After deleting the extra school district tax form  log out of the program. When you log back in, use the Delete a Form tool to confirm the extra school district tax form has been removed from the list of forms in your return.