As children grow and develop their skills and confidence, they are able to take what they have learned in 4-a-side and use it in bigger games.
An 11-a-side game has 20 outfield players most of whom are not involved at any given moment. Even at 7-a-side, there are 12 outfield players with rarely more than half active at any time. How many touches do kids get?
So playing 5 or 6-a-side means up to four less players, up to 50% more touches and most players involved most of the time. There's plenty of time for 7-a-side later.
We still keep using 4-a-side as well because it's a great learning format and because the kids really enjoy it.

The less players
on the pitch,
the more touches
kids get,
the quicker
they develop