Problem is that at this age, kids should be spending a LOT of time in practice on skills, 1v1, 2v2, 3v2, etc.
In order to teach "building out of the back", you need to spend quite a bit of time rehearsing patterns and off the ball movement. It can be done. But if a kid can't collect a pass or pass properly, all of the pattern play in the world won't matter much. And for proper pattern play, it really helps to have a kid play the same position all the time. Not really best for overall development.
Pattern Play Example:
Keeper rolls it out to an outside back, who should be pretty far back. I've seen some of these outside players positioned really close to the BOL. This gives them no time to collect and think.
As the outside back receives the ball, the center mid makes a checking run to the top of the box. The outside mid stays wide. The center forward positions himself between the center mid and outside mid.
If the outside back plays to the checking center mid, that center mid can either turn, or play the ball back to the outside defender on the other side of the field, who then should have some time to dribble out and utilize the switch to get forward. If the checking center mid is covered, the outside mid or the center forward need to move to get open closer to the ball.
Here's a pretty good session on how it can look at practice:
But again - If your team can't get a decent touch on 75% of passes coming to them, all of the pattern play in the world won't make a difference.
Before the BOL, teams had a kid that would try to hoof it over the top. Some teams had this player, many don't. So a goal kick was usually an advantage for the other team. They just had to sit on the top of the penalty area and wait for the ball to hit them in the feet and then beat the keeper 1v1. Teams would try to counter this by having 3 kids inside the PA to help recover once the other team won the goal kick.