The report said 3-foot-11 Gabriel Poirier was wrapped at least four times in the blanket on April 17 with only his toes sticking out, The Gazette newspaper reported from Montreal.
The boy had made noises and was disturbing his classmates in St. Jean sur Richelieu, southeast of Montreal and was warned twice by the teacher to calm down, the report said.
When he didn't, she wrapped him in the weighted blanket and placed him on his stomach. When she checked on him 20 minutes later, he was blue, the newspaper said.
The boy's father had a news conference Thursday in Montreal to denounce the teacher's actions.
"He was only 53 pounds. He was so small," Gilles Poirier said. "How can they wrap him up like that in a 40-pound blanket? How can this treatment be tolerated?"
The family is preparing a lawsuit against the school, the father said.