Hey, you ttt your thread again before it gets knocked off the first page and I'll slap you with a ban so fast it'll make your impatient little head spin.
The easy answer? make sure he enjoys what he's doing, lifts with good form, and isn't forced into it. The same general rules for exercise exist for ALL humans: compound exercises, Focus on progress, keep your form good, rotate when you stagnate.
For kids, Ross Enamait's programs are the easiest cookie cutter solution for both strength and power, but you could easily put him on a program like the one in the stickies, keeping the reps 3-5 reps higher per set for a couple years.
But seriously... if you're this impatient on an internet forum, where the outcome doesn't have detrimental effects, I don't know that you should be training any 9 year old.