What category do I choose for Box 14 for Ohio School District Income Tax?

You need to "get a handle" on what's going on. 

Are you saying your employer withheld income tax for the School district (SD) you live in , but reported the withholding in box 14 of your W-2?  That would be wrong. You need to get a corrected W-2.  But that is SO WRONG, that I wonder what else is wrong.  SDIT withholding goes in box 19 of the W-2. Employers should only withhold SD income tax (SDIT) if the employee lives in a district with a tax. SDIT should not be withheld when an employee only works in an SD with a tax.

As @Hal_Al stated you need to get with the employer to confirm the withholding is correct.  If you check FAQ 12 from the OH Department of Revenue, they realize that sometimes employers put the OH School District withholding in box 14.  It does belong in box 19 and the OH SD XXXX to box 20.  Box 18 should match your box 16 state income amount. 

If the withholding is correct and the employer does not correct your W2, then you can put the information where it belongs in your TurboTax W2 entries in the federal "Wages & Income" section.  Then, in the OH state interview in the "Other Tax Situations" section you should select the "OH School District Taxes" topic to generate an SD100 and the withholding entered in box 19 will be applied. 

Additionally, according to FAQ 13 in the link, if the withholding occurred incorrectly, you correct that by filing the OH SD100. You can put the W2 information where it belongs in TurboTax and then in the "OH School District" topic enter the full year residency dates and then when asked to enter income to be taxed by that district enter zeroes (0) in the boxes and the withholding will be refunded.