Young players DO NOT "get it." Young players DO NOT "get it." Even accounting for ADD/ADHD (which are real), young players need constant checks on understanding with repetition, feedback, correction, and more repetition and feedback.
What you and I know doesn't matter; only what THEY 'get'. I cut my teeth as a defensive player, but we have to work 80 percent of our time on offense as younger players don't have the scoring or shooting skills early on.
I'm sharing concepts from Lawrence Frank. I know my players DO NOT get it, yet...not even close. We don't communicate anywhere close to enough and we're mostly afraid to get beaten defending on the ball.
Frank emphasizes positioning, reaction, and communication...with triangle protection away from the ball. Obviously, the NBA (with a shot clock) is a screen-and-roll league.
"Know the coverage; trust the protection."
This mandates NO MIDDLE stance. Most bigs are not huge perimeter threats early on.
We don't see so much FLOPPY-like action. We have to deny as much as possible scoring in the paint. Most people teach "lock and trail" technique on the ball side and go under the screens on the help side (will always be 'weak side' to me).
High ballscreens will be an issue at all levels. His concept of the ball "pulling" makes sense.
Doubling the post means opening up other areas. Decide whether you'll allow the ball back out to the entry...or understand the helpside perimeter diagonal pass is available.