Truth be told, from the information gleaned in this case, I think that the assault against this teen that occurred on school grounds would likely face an uphill battle in any jurisdiction - let alone New York.
And here's why:
This was a targeted, criminal act by third parties - i.e., non-school personnel. Therefore, unless this student would be able to prove via competent evidence (rather than abject, rank speculation) that the school was aware (or should have been aware) of an impending danger to its student (the plaintiff), yet failed to take reasonable precautions to prevent this violence from coming to fruition on its grounds, the claim will probably fail.
As noted in "How a School Can (Not) Be Liable for an Assault Under New York Law," this is school assault law 101.