The incident took place around 9 a.m., Thursday, Dec. 4, outside of Mepham High School on Stewart Avenue, according to Long Island News12.
School officials told News 12 that the man was in his 20s and driving a small white car.
Nassau County Police said they did not have information on the incident.
School Principal Eric Gomez said: "We will continue to reiterate stranger danger safety responses to our students. As always, the safety of our students is our top priority," News 12 reported.
Click here to follow Daily Voice Suffolk and receive free news updates.