I play first grade (but women's, lol) and really, it doesn't take up too much time- depending on who you're playing for and where you live (travelling time, basically). My weekends are sometimes stolen by Bathurst and Nowra -____-... Tuesdays and Fridays I can't really do much study (get home at 5 from school, leave for training at 7ish, get back 9.30ish, sleep lol) but I just make sure if I have something due the next day, I do it in advance.
Two of the girls in my team are doing the HSC this year, and I know for a fact that they're both extremely dedicated to school (One attends a highly ranked selective highschool, other has been dux of her year all throughout highschool) and they still manage to perform well on the field.
Basically, you should be fine : ) I've never played state outdoor, but I played for NSW in Futsal and its only a few hours of another day of your week gone. I found for that though, there was less emphasis on fitness and stuff and more tactical plays or defense formations etc. So you don't have to worry about getting burned out or anything.
On a related note, aren't you a bit late lol? Or are you talking about a 2010 season?