NEW YORK, Sept. 7 (UPI) -- A New York City woman says her 5-year-old son was sexually molested by four classmates at the school where he was attending kindergarten.

The mother, who lives in the Astoria neighborhood in Queens, filed a notice of claim Aug. 27, signaling that she plans to sue, the New York Daily News reported. She said her son, who wears ankle braces, was jumped by four classmates in a bathroom June 11 and pinioned while they pulled his pants down and stuck fingers into his rear end.

"I'm very sad and disappointed," she told the newspaper. "You never expect this to happen to your child, especially in school. You expect them to go to school and come back safe."

A criminal investigation was closed because of the age of the alleged assailants, and city education officials say their investigation is still in progress.

"Basically, you got four monsters out there who are getting a free pass," Sean Serpe, the mother's lawyer, said. "They haven't even been required to receive therapy for their actions."

The 5-year-old has been transferred to another school for safety reasons. Serpe said the boy continues to have nightmares about the attack and is getting therapy.