Start by sorting your tasks by priority. School is obligatory, and sleep is required for your health, so emphasize on these two points. If you need 8 hours of sleep to feel good and you need to wake up at 7am, plan accoridngly.
I am unable to know whether you like excercise or friends more, but I advise you to learn how to say "no" to an invitation of your friends. It is probably harder than it sounds, and even I am struggling with it, but it should be beneificial to you. And it will make more room for other activities.
In case that you have various tasks to attend to, group them and plan them in with other tasks which are located closely to minimize the amount of time needed.
I am unable to know whether you like excercise or friends more, but I advise you to learn how to say "no" to an invitation of your friends. It is probably harder than it sounds, and even I am struggling with it, but it should be beneificial to you. And it will make more room for other activities.
In case that you have various tasks to attend to, group them and plan them in with other tasks which are located closely to minimize the amount of time needed.