Well I was the same in the summer, going to bed at around 5 and waking up at 2pm, But I managed to get back into my routine of waking up 7ish for college and going to bed at around 11/12.
I think the best thing is too go to sleep soon, set a alarm for around 9/10 that way your body will get use to waking up at that time and then will get up at the time you need to for school.
I did this, or started going to bed a bit early, I managed to get up earlier too and in the end my body just naturally woke up at 7am every morning.