how to concentrate?

recently,i find myself fail to concentrate
i find it hard to do my homework, revision
i am lazy to think the solution when
i came across some problems
i may just put it away and
telling myself not to think anymore
or waiting for the answer to come itself
today i listen to a teacher/pk's 'talk'
he had looked at our results and felt worried for us
he would like to know the problems we are facing
and finally a conclusion is that we all sleep too much
maybe he is correct because among 48 students
only 4 of them said they dont sleep at noon
but i dont think this is my main cause
i now have control my time of sleep
i make it to about 30 minutes or sometimes more
but then i feel tired n less energy when i come to school
is it because i dont have enough sleep? i am not sure about it
then he set a time-table for us
which we need to study at least 4 hours a day(from 4-6pm n 8-10pm)
haha..i know how to plan too
just that is my planing working?
but i could see most people start doing their revision
they also put their effort and i believe no one likes bad results
when everyone is changing, how about me
getting worst and worst
i should have cut down my time surfing the net
and stop finding problems to myself
i am really very good at wasting time