Ontario discontinued its tuition credit for the 2017 tax year.

Effective for 2017, Ontario students can claim the provincial tuition tax credit for eligible tuition paid for studies up to and including September 4, 2017. If you went to school during this period, be sure to complete the column for this period on the T2202A entry step in TurboTax. Then, TurboTax can calculate if you have any unused provincial amounts to transfer.

For example, if I want to school for 5 months, from January to May, and my total tuition was $25,000, I'd put the same amounts in the second column too.

You're exactly right, as I now have finally figured out.  It's too bad, as the student went to school big time starting September, 2017 and well into 2018, and Ontario won't help at all.  As our family is doing fine, it will be another example of better off people getting fewer tax breaks in order to support poorer people who will be able to apply for a grant and get the entire tuition paid for, which beats any tax incentive.  I just hope that most will actually GO to college, as now it won't be THEIR money.