R.S.
It's been a while since I was in school, but my mom did something for me that I now think was genius. She sat me down with a calendar for the week that was laid out in 15 minute increments. The non-negotiables were already filled in (8 hours of sleep, dinner with the family, church, school, etc.) and she had me fill in the rest.
When I took her my schedule as my teenage mind saw it, she reminded me to include time for getting dressed, showered, travel time, meals, and other stuff that I just didn't think through at that age. When it was laid out on a calendar like that, I realized that I really couldn't do all the activities I was participating in and still get good grades. When she presented the calendar to me, the deal was that I had to find enough time to do the activities most important to me and still get good grades or else I had to drop everything. That empowered me to decide what I could and couldn't do but still gave my mom some say over it as well.
This may not work with everyone, but it was an eye opening experience for me as a kid.
Good luck!