You're silly for posting that question in a forum that is for "some" people who eat breathe and live school.
2-5hours is excellent if you're being productive anyway (i.e, no distraction, immersed in work)
I did 8 hours yesterday, 2 hours today. I learnt more today because I wanted to study.
Depends on what subjects people do anyway....
I've put my flamecoat on, but some subjects aren't very study intensive... think physics, geography, business studies. If I were doing any of the above, my work rate would be up by 3 hours....
NOW STOP COMPARING YOURSELF TO OTHER PEOPLE AND FIND YOUR PRODUCTIVE WORKING PERIOD!!!