toomuch00, AP is an advance placement exam. If you don’t know what they are, chances are your school doesn’t offer them.
You can volunteer at many clinics without any problem (you may need working papers and/or parental consent). Call up your local ambulance and see if they take volunteers. You won’t be doing the “exciting” stuff like administering care – you will likely be doing errands and paperwork. But it is great resume building and good for seeing if the work is for you. You generally don’t need experience.
You can also look into taking first aid, CPR, and possibly EMT certification (you may need to be 18 for that, but I’m not sure).
From talking to a few PAs, it doesn’t sound worth it to me, but definitely do your own research. A PA is neither here nor there and many people don’t trust them as much.