The best 10U coach in our rec league (now onto assistant coaching travel) last spring did a ton of fly ball tracking with his players. His team beat everyone based on their defense throughout the season - not just because of that, but in general because his defensive focus.Kids at this age have probably seen very few real fly balls in the outfield. I noticed this fall when we tried some outfield drills that pretty much every kid, even the good ones, were tricked by balls over their head. They just don't see it enough. I started throwing/hitting every ball over their head, just to give them reps of seeing that. Started telling them to think first step back, or at least angled back. They misjudge a ball in front of them, maybe it's an extra base. They misjudge a ball behind them it's probably a home run.