I would think that most of the country considers 9/1/01-8/31/02 as an "on age" 2020. NY does have a different school cut off though. And, really even kids with August 01 birthdays aren't that bad, but when you are talking about 2000 birth year or early 2001 they would be significantly older for a "typical" 9th grader
The entire country doesn't consider this at all in HS, which is why the entire country goes by grad year.
