What should I do for exercise during the school year?

This summer I have been swimming laps, playing tennis, and biking every day. This is because I have vast amounts of free time in the summer.

However, during the school year, I fear that this will really not be possible. I have many after-and-before-school activities, such as seriously pursuing the violin and training for my Bat-Mitzvah. Since the school day and homework and long-term projects take up so much of the day (I am just entering high school), I don't know if I will have any time to exercise on a regular basis like I have during the summer.

Are there any recommendations about how I should continue to exercise during the school year?

First, use P.E/Gym class to the best advantage. If the activity doesn't involve a lot of action, ask if you can run laps first or something.

By planning your time and cutting out unnecessary minutes spent texting, emailing, calling, etc., you can usually find a bit more time than you thought you had. This means all day long, doing a bit of homework when you have downtime in class, making full use of any free periods/study halls, etc. If your fitness is a priority, shaving off time from after school homework will help you build in time for a workout, even if it has to be short most days. If you can use Saturday and Sunday for bigger workouts, and find time on other days for as much as you can (but don't even hope for more than an hour, and aim for 30 minutes 2 days a week), you will have time to get in enough. Be sure to eat very healthy amounts so fatigue doesn't wear you down!

When i was in high school i used to wake up really early and run before school (like, 5am). This worked out pretty well for me. Or, you could try to go out for a sport? Cross country, track? That would keep you in good shape...unless you're too busy with other activities.

What you should do is find some time (maybe between violin and homework) to go for a quick job or bike ride. Even if you can't dedicate the recommended hour every day, at least get in as much as you can. It's better than nothing. :)

Join the swim team or tennis! IF your school is small and doesn't have them, most schools let you join another school's team for that sport.

Or take P.E class.

That's what I do. During the summer I have time to exercise myself, and during the school year, i don't as much, and I'm also a lot less motivated since my school is really tough and we get buttloads of work so I have a hard time pushing myself to physically work too once school is over.

So I take competitive P.E every year, even though I got all my P.E credits a longgg time ago, and second semester, I do soccer, because when you join a school sport, it doesn't matter if you're motivated or not (well, it does...but thats not the point). You have to go to practice and push yourself and organize your time around it no matter what.

Fitness during the school year is tough!

I know it can be so tough to seriously pursue a musical instrument and keep up activity (more than most people think!)  

Something that is great to get in the habit of doing  is incorporating exercise into your practicing routine.  For example, let's say you practice for an hour, then go jog around for 20-30 minutes, practice for another hour.  Or, every 30 minutes, take a 10-15 minute break where you do simple weights and crunches.  Not only does this help you to fit in your exercise, it also gets you in the habit of taking structured breaks while practicing (which help prevent injury).  Also, I have found that the awesome mental benefits from exercise help so much with focus while practicing.