see if you can get into an emt-b class your junior or senior year. see if any local departments have an explorer post to get your foot in the door for some basic training. look into getting a fire science degree after you graduate, so while in school now work hard to keep your grades up.
Dont get too worked up about a fire science degree. Every pro ff that I have spoken to that went to school and got a degree says it didnt do shit for em. Unless you are working for a dept. in a huge city, fd's are pretty much hiring paramedics only. The fact is the future of the fire service is EMS. Sure we will always have fires to put out and cars to cut up but compare how much EMS we run now to what we ran ten years ago. You never used to see a fire engine respond with an ambulance to a medic call, now you see it almost all the time. You also never used to see engines that say "paramedic unit" on the side of them. Point is... train your ass off and get a medic cert. thats what fd's are after
The smaller dept around my neighborhood hire only EMT-P and then train them to be FFs. FF-1 is desirable, but not required. I doubt you could get hired at 18. But you could probably get your EMT-B right after graduating from HS and the get your EMT-P.
I would seriously reconsider your statement about college. You will probably be competing for a very few possitions and a lot of those applicants will have that degree. Plus, a college degree will usually mean more money in your pocket. 2% for an AA and 4% for a BA. Those degrees don't even have to be Fire Science's either.
Go get your EMT-B and get some experience working on an Ambulance. Then go get your Medic. It will put you one step ahead of other candidates. Most Departments that hire medics really want "experienced" medics.