I don't know what co-op is? But, most states require one to be eligible for certification or license to be at least the age of 18, as well most professional services one to be at least 21 to 23 years of age to operate emergency vehicles.
Good luck, and explore your options and schooling.
There is another idea to look into,try joining a medical explorer post in your area. I was a member of one that was sponsored by the local medic service,I learned alot from it.