I've been running for nearly four years now, and I am going into my senior year of high school. I wish to run in college (D2 or D3) as well. I see myself running lots of marathons in the future, as soon as I'm done running in college. Could it be possible to run a marathon next summer, or even in the during any other given summer?
Possible? Yes.
Counterproductive to getting good at college distance events? Also yes.
You'll have plenty of time to run marathons after college, don't bother getting distracted now if you actually want to run competitively in college. (For example...marathon specific training really doesn't require any workouts for several months faster than 10k pace. All races in college are less than or equal to a 10k.) You will not get faster at college events running a marathon, it may even make you slower.