Wait a second.... you got the job right out of HS, with no college, and turned out pretty decently right? What is stopping the OP from being the next hometownmedic5, or Akflightmedic?
We talk so regularly about raising the entrance requirements to our thing to improve the quality of our candidates. One of the principal reasons I'm in favor of adding a degree requirement(a position I support even though I don't hold a degree) certainly isn't the English composition credits or the environmental science course electives attached to a degree. It is that a degree takes time. Setting aside child prodigies, you're not going to college before you're 17/18. Two year associates and you're at least starting to get a handle not he whole faulting thing.
18 year old emts terrify me and I also wouldn't be in favor of hiring them. Sadly, at least on the commercial side, we cant live without them...
Honestly, this type of age discrimination is one of the things that does piss me off. This person isn't ready for a job because they are too young. Age is a simple number, and often an arbitrary one. It's the same BS line of "your only a teenager, only in your 20s, there is no way you can be a supervisor or in management, you aren't ready for it."
Provide objective goals. Earn your HS diploma (I know this might shock you, but there is a HUGE difference in being a HS student and being a HS graduate; ditto being a college student, and being a college graduate). That's an objective goal completely unrelated to the age of a person. If that's your baseline, good.
18 year old EMTs don't scare me any more than any new EMT. Whether they are 18 or 40, they are still new EMTs, and had to pass the same requirements. They still have the same knowledge, education and experience (relevant to the job). Who is scarier: a 17 year old who just get their driver's license, or a 37 year old who just got their driver's license? they have the same level of education and experience behind the wheel. The baseline education standard should be the same, regardless of the chronological age of the person. Arbitrary numbers (if you aren't 30 years old, you are too young to be an EMT) don't help anyone.
give a young person clearly achievable goals, and they have a path to success; make those goals related to something he or she can't change and you will cause that person to ignore you.