KJB - as others have said, kids practice in a structured way in other sports at that age (and much younger), so there's nothing wrong with doing the same with running, if they want to.
I've been through this and have some pointers:
1. The single most important thing they need to learn is how to run properly. I'd try to get hi into a sprint squad once or twice a week, even once a week is enough. That will teach correct posture and form, and will be constantly reinforced if they do it every week. If you don't have the expertise to coach this, find a squad, esp one with others his age so it's fun and he develops friends in the sport.
Distance running form is different, but I can tell you that developing a relaxed, fast, efficient stride is almost as important as the actual aerobic conditioning work. This is harder to coach and teach, but the best pointer is watch a diamond league middle distance race, and watch their form, esp the Kenyans.
2. Core strength is important for all kids sports. Find a good core program and have him do it 2-3 times a week. Work calves, knee stability, glute strngth, quads, abs, plank, back, some push-ups. No weights though, only body weight stuff.
3. The theory at that pre-pubescent age is that kids can train for speed and aerobically, but shouldn't do much in between (speed endurance or lactic work). He'll need to do a bit though. I'd recommend this:
- one sprint session a week
- one longer run a week, mixing 3-4 miles @ 7' pace, with runs building pace as you go
- one interval type session. This could be 4 x 800 at 3km speed, various fartlek sessions, and some 400s at 1500 speed
- 2-3 core sessions a week
After a month of this you should see noticeable improvements. He could easily drop 10-20 seconds off that 1500 time in a month.
How long till his goal race?