Saheam King, 19, of 15 Levey Blvd., shot the girl in the leg at 1:25 a.m. July 11 near the parking lot on Tower Street, close to Allison Court, police said.
Det. Sgt. Steven Bluethgen said King was arrested without incident in Wyandanch early Sunday.
King is charged with second-degree assault and first-degree reckless endangerment, police said. He is to be arraigned today at First District Court in Central Islip.
The shooting was the latest of several violent crimes near the school that have led some Huntington parents to call for its closing. After a shooting March 11 a block away during school hours, Huntington Superintendent John Finello said the area's safety was compromised.
Witnesses told police that the party was breaking up after a handful of small fights when someone fired shots, sending partygoers fleeing.
The girl was treated for a nonlife-threatening leg wound at Huntington Hospital.