Traditional School Districts tax a percentage amount on the Ohio taxable income, based on Lines 19-23 on the SD 100.

Earned Income School Districts tax on all earned income, based on Lines 24-27 on the SD 100.

The AGI is just the starting point for Ohio, and the $300 in charitable deduction on the 1040, reduces the AGI so it will not equal the W2, box 1 totals.

There should not be any error if you let the software do it's job and not override fields.