Some people work at pharmacies during the school year a lot, some a little, and some don't at all. Count me in the last group though I do plan to work during the summers🙂
It's vital to have experience in the pharmacy before graduating, but you have to evaluate your limits and not have work be a burden that lowers your GPA in pharmacy school.
It would be a nightmare having to reapply after failing out of pharmacy school, but working and going to pharmacy school has been done and is possible.