Depends on a lot of factors -- morning vs. night chronotype, how close work is to school, how close school and work are to housing, how many hours work demands, whether your landlord is insane and kicks you all out with 3 days notice right before the semester to rent to a family, etc.

I would still have worked most if not all of my summers, but never more than 5 hours a week during the semesters. My job, which I actually really liked, demanded 20, which also required another 6-10 hours commuting on top of 5-8 hours of commuting to school.

I had also worked in tech for a year before starting school, so I was a bit less worried about having experience to list. And in the end it didn't matter because I started a company and ran that for 5 years instead.