How do i correct back my body clock where it used to be?

Alright so its like this. Its the holidays now and i have been sleeping very late because i want to have more fun before school reopens again. But the thing is, these days i have been sleeping late like about 6~7am plus and waking up at 5pm plus(Yes i just woke up). I tried to correct my body clock by sleeping early, like about 3am to 4am, but i could not sleep, and then when i checked my clock, it was already 6am! I'm worried about how i'm going to get back my normal body clock to go to school when the holidays are over... I always wake up at 7am, prepare to go to school and at night i sleep at about 11pm or later. I want to have my body clock fixed at this timing before school reopens. Is there anything i can do? I do not have sleeping pills or whatsoever...