I understand that a student from Ontario attending school in Quebec, can be considered a resident of Ontario but is this optional?
If advantageous to file as resident of Quebec, can that be done?
If the student is in receipt of monies from the Gov’t of Quebec, they are considered to be a resident of Quebec and there is no option.
If the student is in receipt of a Releve 31 from the landlord or has any other another Quebec ties, the Quebec gov’t will be calling. Be prepared to justify your position, in French. They are looking for scofflaws.
If they are a resident of Quebec, there is no provincial transfer for tuition to the Ontario parents. But there are more credits available to them. Those credits do not transfer when they move back to Ontario, so be prepared to have an Ontario employee, just out of school, who does not pay any Federal taxes but does pay Ontario taxes.
You will have to evaluate the situation based on facts and the long term plans for both the student and the parents.