Handicap stuck at 17

Im twice your age playing twice as long and have a higher handicap. You're in great shape! You'll both gain distance as you grow and through your own development as a golfer. Post a swing in the Member Swings section and folks will help you with your technique. You're doing great as it is!

Sure, but working more on your legs and your abdomen...and much much more important than this: your swing!

Absolutely. Check out the fitness forum on here for ideas. If you work out, obviously you should aim for balanced workouts, but definitely work on rotational exercises and exercises that help you become more explosive, like deadlifts. Just make be careful with weights, since you're at the age when your growth plates might not be fully set. I'm sure you can talk with someone at school or a gym for guidance.

Careful... How tall are you in relation to your parents and siblings? Growth spurts usually begin around 13 and end at around 17 in boys. There is a plus or minus of 1 year. Your growth plates won't be fully set until you're around 18. 16 for girls.

You can get a Swiss ball and do squats against a wall with your own body weight, and that will strengthen your glutes and quads. A great one is doing squats (no weight) on a wobble board. This will help with balance and coordination. Crunches and any abdominal exercise work is good.

And hand strength was recommended as well - see strong hands also mean strong forearms and that's necessary for getting a good hinge - so I highly recommend this stuff - Powerputty - I had to use it for physical therapy, but you work your way up in density. Hand therapists use this stuff in the treatment of tendonitis. It comes with exercises.

Very important point.  You don't want to end up like KJ Choi (who trained as weight lifter until he turned to golf at age 13).

You have to learn your game and make adjustments.  Where do you miss? All jokes aside, read some of the reviews for Lowest Score Wins.  The book is really great especially for someone in your situation.  It will help you examine the way you approach the game.  I know it cost and I feel like I'm trying to sell you something, but I have no reason to recommend something to you unless I believe it.  I wasn't going to buy the book until I related it to playing and paying for a practice round of golf.  It's the best thing you can do.

On a different note, the easiest change you can make isn't to your swing.  Simply play a round on a slow day and drop a couple balls at certain yardages and dial those in.  Also take note of where you consistently miss the ball and play to the safe side of greens.  Take hazards out of play as often as you can.  Make sure you can get near the green in regulation (nGIR) and work on getting up & down to save pars...

The difference between a 17 handicap and a 10 may not be anything to do with the shots they hit and their swings, it may simply be the way they approach the course and what they know about their shots types and the knowledge of their own game.