While I agree with most of the posts so far, I'd have to say that first you need to develop the neurological aspects of running, form (efficiency) and strength. Start with form drills and hills.
Mileage is not the most important factor for the youngster (pre-high school), form and speed development is. If you can get that ingrained early the rest will come in a well balanced high school program.
Recovery days need to be recovery days. I know some youth coaches that want complete rest, no running on those days (if those kids are multi-sports kids I agree with that). For us those days are your mileage days, and it's never about mileage it's about time spent running. That time spent on a recovery run is based on their age, fitness and talent. It's my experience that Kids have an easier time accepting training when you don't measure mileage in miles. I continue to use time spent running with the HS kids I work with.
Teaching percentage of effort is really important for a young distance runner, most young distance runners are smart kids and understand Math and Science, it's fun for them to understand what they are doing and why.
Ingrain the quick turnover aspect into training, I see way too many kids with a long loping (bounding) stride coming into high school, when those kids finally get the quick turnover aspect into their training their races really start to come together.
My college coach Jim Hunt has done a lot of work developing programs for youngsters, he has a video that is priceless. Others like Coach Jay Johnson have redeveloped Jim's and Vern Gambetta's Ideas to fit the world class runner. The ideas are basically the same: VO2 max work and strength work make a better runner:
http://www.coachjayjohnson.com/2009/03/anatomy-of-a-workout-002/
Jim Hunt's Video:
http://www.runninaway.com/?id=video