You're going to have to complete a 4 year undergraduate degree before you can matriculate into PT school. So that gives you 2 years left of high school, 4 years of college to get through. Don't get ahead of yourself. Focus on getting good grades in AP science classes like biology, chemistry, and physics as a high school student.
Find an undergraduate program and degree you would be interested in - there is no pre-PT degree. You will have to major in something and most people on this forum recommend against majoring in exercise science as you would not be able to do much with that degree if you don't get in to PT school or don't end up wanting to be a PT. In order to find the best fit for you, you will need to do your own research. Does your high school have college advisors? Make sure as a junior you get a meeting with a college advisor to help you select the best fit - they will be able to tell you about available scholarships as well. PT school is a lot of money and time, I would definitely consider the additional cost of undergrad before choosing a college. Do you want to be applying to PT school already with student loans on your back?
When you do attend college focus on excelling in your science and pre-req courses. I finished my pre-reqs (after getting my college degree in art) in about a year and a half worth of semesters. You don't have to only take science courses. Be a well-rounded person and take classes you enjoy and develop other aspects of your personality. Maybe try a course in education, music, poetry, philosophy, art. Perhaps you want to be in the athletic training program and help the college athletes. There are many options available, but don't get too obsessed and one-track minded with PT. Do other things with your time: find research assistant opportunities, try intramural sports, be a part of a club or two, volunteer with underprivileged kids, develop real relationships with a couple of professors who will be able to give you great recommendations.
You have a long way to go before attending PT school. Set yourself up with good grades in your pre-reqs so that you can apply if you end up wanting to do so, but things could very well change for you in 6 years and you don't want to end up a 1 dimensional person who has only thought about a career in PT his/her whole life. You're still developing as a person. Be responsible and take action - don't look to your parents, teachers, etc to do the work for you. Research the program you want to get into (northwestern?) and create a step-by-step plan of what you will need to complete to get there. Good luck.