How to stop being tired and sleepy?

I wake up at 6AM for school. During classes I have a hard time listening or concentrating to the teacher. School finishes at 5:15 PM or sometimes we're dismissed beyond that. When I get home I eat dinner, take a bath then I start studying or doing my homework. A few minutes later I get really sleepy but sometimes I try to stay awake and sometimes I drowse off! I really hate it when I drowse off! It gives me less time to finish studying and do my homework! because of that I have to stay up to 12 AM. So do you guys know how to stop myself from being tired and sleepy? Not coffee please I don't like to start drinking it at 15