Maybe I'm just crazy, but it sounds to me like your teen might simply have too much going on. I think we tend to over schedule our kids from a very early age and not let them spend enough time just being kids.
The policy my parents took was to allow me and my siblings to choose two and only two extracurricular activities. (A part time job counted as an activity). This allowed us to manage our time better and also taught us how to prioritize. I chose to focus on drama and student council when I was in High School and I feel like I excelled in both because I didn't divide my time in a thousand different ways.
This approach also really helped me to understand how much my parents valued my education. They knew I didn't want to work part time, and they agreed to help me pay for things (in moderation) as long as my grades stayed high.
Because my attention was more focused, I was able to achieve a lot more success in my chosen activities than I would if I had tried to pursue everything that caught my eye.