PUEBLA, Mexico—When Lupita Pérez Parra was a young girl, struggling to learn how to read, her mother would punish her by pricking her fingers with a sewing needle. Years later, when Ms. Pérez became frustrated at her own children, she found herself meting out the same painful punishment.

Only after her family nearly fell apart, and after years of family therapy, she says, did she realize she was merely repeating a generational cycle of abuse, disciplining her children the only way she knew how: with threats and violence.