The key to improving young soccer players is to get them touching the ball more often. Playing 11 vs. 11 at training is going to limit the number of touches for each player. And the better players will naturally get more touches. So the players who need the help most will touch the ball less, and will get bored and feel like they do not belong. This will be particularly evident if you have a team with widely differing abilities. Your goal during training as a coach with your soccer drills should be to maximize the number of quality ball touches for each member of your team. Small sided games will help you to do that. If you still have one or two players taking over these games, limit the number of touches before they have to pass or reorganize the teams.
Small sided games help with player development as players get to spend more time in both an attacking and defending role. In an 11 vs. 11 game how much time does each player actually spend involved in the game. In reducing the field size and the number of players, players will spend more time involved in the game, and they will have to transition more often from an attacking role to a defending role. As a coach you should encourage them to remain involved in the small sided game at all times. Moving into space after passing the ball, switching to a defending role after the ball is lost, talking to their teammates, and effective passing and dribbling skills all should be emphasized.
Encourage your players to make better decisions on the field. Small sided games at training help players make better decisions on the field by making the decisions easier and less complicated. On a big field with 22 players, players have a huge number of options from which to choose when making a decision. This can make the process overwhelming and will lead to a loss of confidence. Reducing the field size and number of players helps players to make better decisions by giving them fewer options to choose from. Applaud them when they make the right decisions and correct them when they make the wrong decisions.
Small sided games also give the coach a better opportunity to observe each individual player. Observing the respective skills of 6 players in a small environment is a much easier task than 11 players on a big field. What are players doing off the ball? Do they run into space? Are they standing around waiting for the ball to come back? With 11 players on the field most observation takes place where the ball is. So it is hard to observe what the other players are doing. Fewer players in a smaller area make it easier to observe everything that is going on. If you have 2 games going at once with your manager or parent running the other game, you as the coach should periodically swap so you can observe all players.
Small sided games at training are a great way to reinforce the skills practiced during the soccer drills you perform at training. They are also physically demanding so can be a great way to conduct fun fitness sessions. More ball touches for each player, better decision making, more involvement in all aspects of the game will help all your players improve at a more rapid rate. Small sided games are a great training drill.