Well i'm not in school but i do have a two год old to care for. I use it an час in the morning checking my e-mails and making sure my games on Facebook are okay. Then when my son takes a nap around 12-3pm i have a quick game или two, probably go on here and see what's going on. But that's only if i have no other thing to be doing. Then once my son is in постель, кровати and all my chores are done i go all out :) So i'd say about..8 hours...if that.
In the summer it can be several hours if I have nothing better to do. (Around 8-9 hours before I start getting yelled at.) But I share the computer with my entire family, and my sister is a computer hog, as well. Sometimes I'm only on for an hour, but usually if she's on than I'm not on at all for the entire day.