Morelos state Human Rights Commission president Fausto Gutierrez says the 11-year-old boy was tied to a chair for half the school day, ostensibly for misbehaving.
But Gutierrez says the child's parents believe the teacher was retaliating against them for joining a movement against the strike.
Teachers in Morelos walked off the job for two months to protest a nationwide reform that prohibits educators from inheriting their jobs from relatives.
The autonomous government rights commission said Thursday the incident occurred at a school in the city of Cuernavaca.
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