Everything becomes scaled down for smaller soccer players compared to the adult game. Kids play on small fields nowhere near the size of a full regulation field 100 or more yards long, with as few as three players compared to 11 for grownups. Even in a league, parents may serve as referees, games may last only 20 minutes and scores more than likely won't be kept. In keeping with this small world, kids' soccer balls are also smaller.
This size ball, the smallest aside from mini-balls not used for real practices or games, weighs 10 oz. and can be used for players under 8. The No. 3 ball is only 24 inches in circumference and thus doesn't come up as high on the leg as an adult model. You don't need to provide a match-quality ball for your young player, write the authors of "The Complete Idiot's Guide to Coaching Youth Soccer."
This 12-oz. ball works for players between 8 and 12 years old and has a circumference of 26 inches, larger than a size 3 and smaller than the size 5. This age group tends to play on a field of about 30 to 50 yards, writes Deborah W. Crisfield in "The Everything Kids' Soccer Book," with a goal size of around 6 feet high and 18 feet long. Again, the scale for the U12s falls between that of the U8s and that of the older age brackets for the No. 4 ball and the game as a whole. Some leagues may limit the No. 4 ball to U10s instead of U12s, so check league rules before making a purchase.
Weighing 14 to 16 oz., a No. 5 ball is the largest-sized ball, and players 12 and older can feel like grownups upon graduating to this size, also used by adults. Its circumference is 27 to 28 inches. Prices can start at $15 for a cheap training ball and up to $150 for a match quality ball, especially if it is a special edition issued in conjunction with the World Cup or Olympics.