The alleged incident happened in March at the South School.
Clarice Stingley took her complaints to the city council Monday night. She says the incident stems from a dispute between her 11-year-old son and the son of the officer.
"He came into their school unannounced, in uniform, handcuffed my son and told him that he was gonna lock him up for the rest of his life," said Stingley.
"We interviewed the staff, some of the kids that were nearby in proximity with this young man, and we have no witness who saw this officer handcuff this child," said North Chicago Interim Police Chief James Jackson.
Jackson says security cameras did not show the alleged incident, and he says the officer denies the accusation.