South Brunswick Police Sgt. Jim Ryan says the 27-year-old pilot and a 44-year-old female passenger sustained chest and back injuries.
Their names have not been released.
Workers who were tarring the roof of the Indian Fields Elementary School told police the copter was spinning in distress and veered toward the school before making a rough landing about 100 feet from the closed building.
The windshield was smashed and the tail section was broken off.
The Robinson R22 Beta is owned by Nassau Helicopters at Princeton Airport.
FAA spokesman Jim Peters says investigators are headed to the scene and no other information is available.