Very simple solution and it worked for me.
the wall push-up
have your youngster walk up to a wall and stand a little under arm's reach from the wall
have him point his feet inward (pigeon-toe fashion) and SLOWLY lean toward the wall supported by his arms until he
can touch the wall with his nose, then, just as SLOWLY lean back away from the wall (If done properly he will feel the stretch in his shins almost immediately)
start with 3-5 reps very slowly and increase to 10
i found this cleared mine up within two days, TOTALLY
Additional note: I clearly cannot speak for everyone but it has been my experience that this is caused by shoes that have soles which are too hard and/or running on surfaces that are too unforgiving. He may need shoes with more cushioning, or perhaps even racing flats since he may be young enough to benefit. He should run regularly on soft surfaces: grass, dirt, trails.