Over the past 2 years I have coached little kids (Kindergarten mostly) in both T-Ball and Flag Football, and keeping score is of no concern to them. My 5 year old has played both and is currently playing basketball and all he is concerned with is having fun and as coach my first concern was to make it as fun as possible and then to try and teach them some sort of fundamentals of the game. In my son's mind, they have never lost a game based on score. I let him believe whatever he wants because it isn't my concern as to what the score is. Usually the first things out of my mouth are "You played hard" and "Did you have fun?" As long as he plays hard and has fun at this age, that is all that matters.

Now as they get older, I think score should start counting. My best estimate would be around age 9 and/or 4th grade depending on how things are broken up. But even then, playing time should be mandatory unless it is an all-star team.