What should be my schedule for running 5K as an experienced runner?

I want to start long distance running, particularly the 5K. I used to be a sprinter and I've had a small taster on long distance running. I've ran two cross country races and I was quite good. I ran 2.5 miles earlier this year and my time was 12:36. I really enjoy running! Anyway to the question, can someone give me a schedule that I can follow so I can run a sub 16 minute 5K. I train a little bit (stretching, small runs, runs around neighbourhood), but I want a real schedule. I would say I'm an intermediate runner. By the way, I'm in my first year of high school! Thanks very much for all answers, very much appreciated!