It has been scientifically proven that the youngest kids in any grouping by age do the worst.

http://upload.wikimedia.org/wikiped...tion_UEFA_youth_tournaments_2010.pdf.jpg

The same pattern has been seen in soccer, baseball, and hockey.

From the data shown, the only "fair" thing to do is break up the leagues by the month the kids are born in. It might involve a lot more travel to pull all these leagues together, but anything else is cheating the younger kids born near the end of the age cut off.