A 16-year-old was arrested early Thursday, charged with robbing a 17-year-old at knifepoint on the grounds of Valley Stream North High School, Nassau County police said.

Joshua Hayes was arrested at his home at 873 Prescott Ave. in Elmont at 1:15 a.m. and charged with first-degree robbery, police said. He faces arraignment Thursday in First District Court in Hempstead.

The proceeds of the robbery were not recovered, police said. Police did not say if the knife used in the robbery or a handgun believed used by an accomplice were recovered. Police are still searching for the accomplice, described only as an unknown male.

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Police said the accomplice approached the victim after he rode his bicycle to the back of the school on Herman Avenue and said that when the teen attempted to make a phone call the suspect grabbed the victim's iPhone6. When the victim protested, police said, the accomplice pulled a black handgun. While that was happening, police said, Hayes pulled a gold and silver knife -- and told the victim to empty his pockets.

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The teen refused and police said the accomplice struck him in the head with the gun.

The teen managed to flee on his bike, police said.

He then called police with help from the school staff and reported the robbery, which occurred at about 4:40 p.m.

It was not immediately clear if Hayes is a student at the school.