Check out Milesplit.com, they have lists. As a former coach I'd say you are a good runner. Jim Ryun ran a 57 400 as a freshman and they cut him from the team at Wichita East HS, KS. (That says more about Wichita East H.S. at that time than it does about Ryun.)
You can be a good runner. Here is an off-season schedule for you:
Sunday: 5 miles/ 4 x 100 strides @ 80-90% (Never all out this early.)
Monday: 2 miles/ 4 x 100 strides @ 80% of top speed.
Tuesday: 5 miles/ 8 x 100 strides @ 80-90%
Wednesday: 2 miles or Day Off
Thursday: 4 miles Fartlek
Friday: 2-4 miles easy
Saturday: Long Run, depending on what you have done in the recent past.
I would think that if your longest run was 5 miles, you would want to stay with that distance for a few weeks before trying to go 6 miles. If you feel good, run fast. If you feel lousy, either run easy, or take the day off.
Always warm up and cool down before running. You can vary the warm up but usually walking, jogging, dynamic running drills, and/or strides should be included. Cool downs are similar but substitute dynamic drills with stretching.
Because you are still young and growing I would be very careful not to over do it. The main thing to do on your own is to run long, and have days where you change speeds a lot. Do not get caught up running the same pace all the time! When in doubt do less!!!
*Warning, this is not a complete program.