as a high school golfer myself:
forget practicing. as long as there isn't one horrible thing in your game which practice would improve, go out and play the teams home course 3-4 days a week afterschool. Play the courses that you often play away as much as you can. Confidence is the most important thing on a course. Get to know the courses you will be playing.
When you play, play by very strict rules. practice how you will have to play in matches. Get a copy of a rulebook and read through it before you go to sleep if you can.
when you keep score, keep track on every hole things like fairway, green in regulation, amount of putts, and penalties(water, ob, et cetera). keep all your scorecards so you know where you need to improve. you can practice on these things when you have time- or if a area is really bad in particular take a day off playing to practice.
Keep it fun and when you are playing in a match, as tiger says the only competition is yourself and the golf course. everybody, including me, freshman year forgets this and plays against the opponents, getting in my head. I think its best to juts be relaxed, focused, and try to go as low as you can without playing makeup golf (o noes he got a par i bogied, o crap i doubled i need to par the next 2 holes... at least his ruins MY game. we are all different)
sorry for the long post but i hope this is helpful