I've managed the same group of underage boys players for the last 3 years. At U11, offside didn't apply, and I didn't concern myself with defensive strategy.
At U12, where offside did apply, I instructed the boys to play a high defensive line, whereby all defenders pushed up to the half way line regardless of where the ball was in the opponents half, and the keeper acted as a sweeper playing at the edge of the box. We had quite a bit of success with this, and maintained it for our U13 season.
However, it didn't work out very well at U13. We came up against faster forwards and better passing, and while we broke up many attacks with the high line, we were caught out too many times.
I'm now wondering what to do at U14. I guess the alternative is to have a "flat back 4", whereby the defenders move in a line up and down their own half relative to where the ball is the opponents half.
My concern here is that the high line discipline is relatively easier to understand for young players. Its easy to instruct them to move to the half line when we have possession. The half way line acts as a guide rule. I think it will he harder for them to maintain their shape if they don't have the half way line to guide, and this will result in "stray" players playing opponents on side.
I am also considering maintaining the high line and have 1 central defender change in and out of the sweeper position when the opportunity or need arises.
What is the standard approach that youth coaches use?