NY age cutoffs for school are different from most of the country. This puts NY at a disadvantage in athletics.

Most school systems are designed so that children are 5 years old when they start Kindergarten. The US Lacrosse age guidelines are designed to take this into account.

A child who is held back, for any reason (academic, emotional, physical, "red-shirting") generally needs to play "up" as a 7th grader as they are U-13 ineligible. 6th graders and 8th graders do not have this problem since there is a one year cushion with U13/U15 designations. 8th graders who are "older" do not need to sit out for a year. They can play U15 along with their classmates.

A child born the last four months of 1999 who is set to graduate HS in 2017 is actually a grade ahead of what is typical for his age. If in 8th grade this boy is playing competitive lacrosse he should be preparing for High School and playing U-15 or 8th grade divisions at tournaments. There is no reason for an 8th grader to play U-13 even if he is US Lacrosse eligible.