I recommend volunteering at your local hospital. It is a great way to understand more about how the healthcare system works, you have an opportunity to give back, and you get to network with professionals in a hospital and learn more about their experience. You may want to also consider joining an organization like HOSA or start a local chapter at your high school.
When I was in high school I volunteered at my local emergency room to see what it was like in a health care setting. I also tried to shadow as many physicians as I was able to. This helped me see which specialities I liked. I hope this helps. Best of luck.