Updated

A mother and her boyfriend shaved the head of her 12-year-old daughter, then forced the girl to wear a diaper and run up and down outside their home near Minneapolis because she wasn't doing well at school, police said.

Police arrested the 38-year-old woman and her 34-year-old boyfriend Monday night on suspicion of malicious punishment of a child, a gross misdemeanor. Lt. Mike Monsrud said the two adults laughed as they were hauled off in a squad car and apparently didn't understand why officers had intervened.

A neighbor called police earlier that evening after a crowd of about 50 people gathered to watch the girl, who was wearing only the diaper and a tank top and was begging to be let back inside their townhouse in Fridley about 7 miles north of Minneapolis.

"When the officer found her, she was crying and hysterical," Monsrud told the St. Paul Pioneer Press (http://bit.ly/KliVgT ). Investigators believe she had been outside for about half an hour before the neighbor alerted police, Monsrud said.

The mother and boyfriend were being held in the Anoka County Jail pending charges. The girl and three younger children were placed in foster care.

The Associated Press is not naming the adults to protect the identities of the children.

The two adults told police they were punishing the girl because she had bad grades and failed to do her homework.

"They told her if she didn't, they would shave her head and put her on 'diaper duty,' which I guess meant running up and down the street and cleaning up trash as a form of public humiliation," Monsrud said.

The lieutenant added that the couple questioned the police's decision to intervene.

"Through the whole contact, and even on the way to jail, both were laughing and thinking it was ridiculous police would get involved in what they said was their parental decision," he said.

Officers had responded to four calls in the past two years at the family's townhouse. At least one of the calls triggered notification to a county child protection worker, Monsrud said.

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Information from: St. Paul Pioneer Press, http://www.twincities.com