I don't understand how schools can't give people study leave, seems so weird to me because I would probably fail if I didn't have study leave. I could only manage like 2 hours of revision after school and I could never revise at school because it was always too noisy.
If staying off gets you into some trouble where it would impact on your future then I would advise going. However, if you really feel like you need it and it will benefit you then I don't see the problem. Just do what you think is best.