In other words you are currently temp resident and now you are seeking to change you status to student. I know for sure that once you receive approval in principle for your PR application you will be eligible to apply for an open work permit or a student visa with the necessary proof of acceptance from a school. I also know that once outside of Canada you can make the same application for a student visa. Your situation is a bit different since you are already in Canada. Personally i don't see a problem since you will simply apply to change you status on the same forum used to extend your TRV.
