The KwaZulu-Natal education department has described a female teacher as an "animal" after she was found to have locked a grade 3 pupil in a classroom overnight - for not doing his homework.

Spokesperson Muzi Mahlambi told SowetanLIVE that the incident occurred at Blessed Luanda Primary School in Donnybrook, west of Durban in the Harry Gwala District Municipality, on Tuesday.

"It was brought to our attention by a witness. We then contacted the school, who confirmed that school management was dealing with the issue," said Mahlambi.

"At this stage we are not sure what time the boy was locked in the classroom, but we estimate some time after 2pm as that is the time school finishes."

He said the department was infuriated and stunned by the news. "This is cruelty at its best. It shocked us as a department that you can have a teacher behaving like an animal. We will continue with our investigations," he said.

Mahlambi confirmed that the teacher has been charged with misconduct and suspended. He also indicated that a case has been opened against the teacher by police.

Education MEC Mthandeni Dlungwane is expected to visit the school soon. 

Police could not be reached for comment.