Adding to what's been said, it's a hard, hard career. I train jumpers professionally and spent several years in Florida as a barn manager and assistant trainer. I knew from an early age I wanted to be invovled with horses in the future, but I didn't know to what extent - trainer, instructor, breeder, manager?
You're very young, and your passion for horses is admirable; however, it's a fairly broad industry. Are you sure you training is the route you want to take? Do you see yourself doing this long term? The majority of horse trainers do NOT make huge figures - how will you support yourself?
I have to agree with Speed Racer in that trainers with upper class clientele typically (and I emphasize typically because it is not always the case, my family did not grow up terribly wealthy but I've been fortunate enough to fulfill my dream) come from money themselves. Unfortunately, a great deal of the industry is who you know and where you come from, a harsh reality.
If in a few years once you finish school you're still serious about it, I would seek out a working student (intern) position and go from there. Get your name out. Work hard. Expect long days, a lot of pain, a lot of falls, and remember, inevitably, you're going to get hurt. For now, I would focus on your studies and keep your horizons open. Good luck! :)