How many hours should I work while at college/sixth form?Watch this thread
How many did you guys work while at college? Tips to avoid burnout?
However long it takes you to keep up with the topics, should be how many hours you study.
In that case particularly if you're basically "full time" in the week, I'd really not suggest more than one weekend day shift (or two short shifts across each day) just to maintain your sanity more than anything else