We should get 7-9 hours sleep a night. If one goes to bed at 3 and wakes at 10-Noon, that's the right amount of sleep but this phase "snydrome" (not something wrong with you, just a pattern) is mostly about young people and/or people working shift work; they have moved themselves out of a bed at 10:00 p.m., up at 6:00 a.m., bright-eyed-and-bushy-tailed for school or work pattern.

Do you not go to school because you don't get up? That can be a problem and it is because you have adapted this particular set of waking/sleeping time periods as "yours". Now they're a habit and you can't adjust to a more usual one for school/work (without a whole lot of work on it to move it to a different pattern).

Normally, people who go to sleep at 10:00 can stay up an hour or two longer every now and then, have no trouble going to sleep, etc. But if you lay down at 1:00, say, you can't go to sleep, can you? Even if you want to. It's about choice of when to go to sleep. If one sleeps 8 hours, say, then one is awake for 16. Trying to get to sleep in the middle of those 16 (or to wake before the 8 is over) is the issue. It is part of sleep habits. Some have an easier time setting them up and others are set up by them :-)