You are only 15 so there's a while to go yet. But you have plenty of time to decide on which therapeutic riding direction may be interesting and maybe get experience as a volunteer to help your decisions. Not quite sure about the english scene now but there is a big difference between hippotherapie K and lets say, riding for the disabled and other ways of using horse and or riding for remedial purposes. Some basic horse qualifications are neccesary or if not I'd advise you to go for them. Google around first to see what is local and realistic to have a visit to. For Hippotherapie here it's physio degree plus Wikipedia reference-linkBobath neurologie courses plus riding experience then the hippo therapie courses afterwards. You might also be interested in Equine physio, possible after a physio degree or there are other pathways nowadays. Looking way into the future for you I believe there is a great need for riding instructors of every level to be able to analyse posture of the rider whether disabled or not to help the horse move better.....turning to use Alexander technique or Feldenkreis methods to help people on horses. Main thing for you is also to keep doing courses in the meanwhile to widen and deepen your knowledge of horses and horse handling skills, more pathways will then be available. Good luck!