I was in a pretty similar spot my junior and senior year. This might seem like the worst advice ever, but:
1.Band is not life and your school work needs to be number 1 no matter what. That being said, if you're doing everything right, you'll have plenty of time to practice.
2. Right after rehearsal, eat, then study. If your schedule is genuinely that intense, cut video games and tv. Doing homework should come before being on your phone (you'll get more sleep that way too)
3. Be aware there will be a few nights where you don't get much sleep. I always set a hard bedtime of midnight. I would also wake up at 5 to finish any homework (you probably don't need to be THAT drastic)
4. In high school, turning in everything on time will guarantee you an A (unless your quality of work is just that bad). In college it will guarantee you a C, but be happy you're not there yet
5. You're from NEISD, and I know their AP curve creates a very competitive environment higher than any NISD school. Don't let it get to you too much, whether your GPA very high or not as high as you'd like.
6. Realize you will never study on the bus to or from a competition. Do your homework before or after competitions.
7. Realize early on that life is unfair and teachers don't owe you extensions.
The plus side to all of this is that taking high school that seriously has made college relatively easy, plus I entered with 117 credits, which made my parents' wallets very happy.