I recognize that NY is December 1, but the September 1 date aligns with the cutoff for schools here in Va, and I am told that of most other states.
As for every year v. every other year age ranges, it has to do with numbers. Clubs in non-hotbed areas struggle to form teams at a single age, and would not be competitive.
Overall, the current system seems to be antiquated. As sport has grown, it would make sense to have clubs governed by a single authority, charged with rules, ages, insurance, etc. USLacrosse needs to step up and respond faster to the evolving issues | 
