You got the computer from your high school? I'm sure they have some way of figuring out your history. Be careful though. There was something awhile ago in the news about a boy who found out his school was spying on kids through their web cams. I just wouldn't put anything personal on your computer.
I wouldn't use that computer for anything else but school cause you know they can find out like in my school I was told (not sure if its true) if a phone or something is connected to their wifi they can view stuff on the phone ... So I always turn my wifi off