A two or three standard deviation intelligence kid can likely understand and benefit from the leadership training that someone 5-8 years older than they are gets. Camp counsellor training, mcdonalds restaurant management training, sports coach and instructor training, military cadet officer training, all programs designed for mean level intelligence people. You just need to give younger smarter kids access to them, and much earlier.

Even just instead of merely teaching kids how to do something, teach them how to teach it while they are learning it. Like, "To do this interesting thing, we need to solve these problems to get there. Here's how to ski, or divide large numbers, we're going to space out the repetitions so your brain will become hungry for it, and when you are showing other people, you can use this method to help them understand faster. Smooth is fast, lazy is clever, etc."