What happens if I change course or fail to make progress as a student in Belgium?

The student permit depends on you being a real, progressing student. Changing your course or institution can be allowed, but it must keep you within recognised study that justifies the permit.

If you make insufficient academic progress over time, renewal of your residence permit can be refused, since the authorities expect studies to be your main purpose for staying. Keeping enrolment up to date, progressing in your programme, and informing the relevant authorities of any changes are the best ways to protect your status.