Robyn it sounds like you are a young woman of wonderful depth and feeling.
Death just isn't easy - ever. I believe that Time and Faith are the only things that get us through a death. There are stages of grief that most people go through. But mostly everyone grieves in their own way and in their own time.
For example, you may decide to continue on with your sax in memory & honor of him. Or decide to graduate with honors so that when you walk across the auditorium you will know how very proud of you is still is.
Don't ever believe that death is the end.
Whatever it is that makes you you, and your band leader who he is, isn't in our bodies. Call it our personality, or soul, our energy - it lives on because it isn't tethered to our bone marrow or brain chemistry.
His is free now - and you can believe that his energy is aware of yours and of the entire schools...
Do something positive with your grief. Grades, the sax, volunteering, just do it in his memory...
Also, write him a nice long letter. Tell him how important he is to you, what you learned from him, how you feel about him being gone. You can add to it, burn it in a little ceremony, tear it up and write another one, but just write it out...
And I'm so glad you came here. Loss is so hard, it's nice that there are places like this to come to.