Most estimates I've seen of funding for New York students is $25k to $30k a year though. I would think that's more of a sign of incredible corruption and mismanagement and not that there isn't enough money to go around.
To compare, Stuyvesant High School, the best in NYC, is $18k per student.
I would argue the point that Stuyvesant is the "best" but I don't disagree with your point. The problem is that a lot of the money ends up in the schools with the rich kids and for a lot a lot of students and schools they never see anywhere near that type of money.
Stuyvesant, like most good schools, raises a good deal of private funds. That actually accounts for good deal of the difference in resources between schools.
To compare, Stuyvesant High School, the best in NYC, is $18k per student.