I'm thinking of staying in for the night.
Taking time to myself sounds like a great idea, is there any reason why you can't do so?
No, I'm going to be able to relax all by myself
As long as you don't have any prior social obligations, it's perfectly acceptable to decide that you would rather spend time at home relaxing rather than going out. It's important to take a break every so often so that you can rest and recuperate as spending all your time studying or socializing is exhausting.
School is so boring and my teachers suck.
Yes, it can certainly feel that way at times, but you know how important school is in the long run.  You should be ready and able to take these breaks when you need them, and you'll be able to get back to school tomorrow.