A second-grade boy found dead in a school bathroom had no known medical problems before his unexplained collapse, his mother said.

Justin Leith, 7, wasn't on any medication, and a July checkup didn't note any concerns, his mother, Nadette Gordon, said after her son's death Friday.

"He was playful, cheerful -- there was nothing wrong with my baby," said Gordon, 27, a home health aide.

An autopsy was to be performed to determine the cause of Justin's death. Police said there were no signs of foul play.

Justin had been excused from his class at P.S. 205 in the Bronx to go to the restroom Friday morning, police said. Classmate Robert Williams said he found Justin lying on the floor when he went to use the same bathroom.

"He wasn't breathing. He wasn't moving," said Robert, 7, who said he alerted a teacher. Justin was taken to a local hospital, where he was pronounced dead, police said.

Justin, an only child, returned to New York this summer after living with his father in Atlanta for about two years, his mother said. Two of his spelling tests, with grades of 100 and 101, were affixed to her refrigerator.

"He's my life," she said. "I love him to death, and he knew that."