The below explanation comes straight from US Youth Soccer:
1. Because we want our young soccer players to touch the soccer ball more often and become more skillful with it! (Individual technical development)
2. Because we want our young soccer players to make more, less-complicated decisions during the game! (Tactical development)
3. Because we want our young soccer players to be more physically efficient in the field space they are playing in! (Reduced field size)
4. Because we want our young soccer players to have more individual teaching time with the coach! Less players on the field and less players on the team will guarantee this! (Need to feel worthy and need to feel important)
5. Because we want our young soccer players to have more, involved playing time in the game! (More opportunity to solve problems that only the game presents)
6. Because we want our young soccer players to have more opportunity to play on both sides of the ball! (More exposure to attacking and defending situations)
7. Because we want our young soccer players to have more opportunities to score goals! (Pure excitement)
These are the reasons why we adults must foster "Small-Sided Games" in our youth soccer programs. The "Small-Sided" environment is a developmentally appropriate environment for our young soccer players. It's a FUN environment that focuses on the young soccer player.
First, It's important to know that the build out line ONLY APPLIES TO U9 & U10 teams and play 7v7.
The Build out line is used to promote playing the ball in an unpressured setting. The bottom line is that when the goal keeper has the ball, the opposing team needs to move behind the build-out line, NOT pressure the goal keeper.