The clock isnt that bad..when you start you're better off doing as many classes as possible, be a model student, cuz when that town opens up you're gonna go on crazy shopping and adventure sprees, I played for 3 straight hours (real life) without touching a simple mission. Once you complete a class you don't have to attend so you'll feel like a senior just wandering around while alot of other kids are in class (Alot of other kids dont go to class sumtimes, skipping or otherwise)
Im in CHapter 3 and there is so much to do right now, and the schedule is never a problem since i only have 1 day that I have to go to class left. You can save some of your classes for later if you want to keep that school feel, but watch out for Truancy..