The incident allegedly occurred May 16 during an after-school program at the Bedford South School, the Canadian Broadcasting Corp. reported Wednesday.
Jennifer Procunier, mother of a 7-year-old boy involved in the incident, said about 10 children may have been receiving punishment for behavioral issues.
She said her son told her they were lined up against a wall and had their mouths taped shut by an assistant instructor.
"This is abuse. You don't do that," Procunier said.
Doug Hadley, spokesman for the Halifax Regional School Board, said the assistant instructor has been put on paid leave, and that Halifax Regional Police are investigating the matter.