Should a student go from having a tax refund to having a balance due after entering tuition credits?

[TurboTaxSusan]

It's possible.

In an effort to get you as many credits possible, TurboTax automatically claims any credits that it thinks you are eligible for. If you worked, but have a low income, TurboTax will claim the Canada Workers Benefit (CWB), which is a refundable tax credit for people who work, but don’t make very much. However, students are usually not eligible for this credit, so when you tell TurboTax that you have tuition, then the CWB is removed if you no longer qualify for it.