Psychology has considered the development of learning, but the development of teaching in childhood has not been considered. The data presented in this article demonstrate that children develop teaching skills over the course of middle childhood. Seventy-two Maya children (25 boys, 47 girls) ranging in age from 3 to 11 years (M = 6.8 years) were videotaped in sibling caretaking interactions with their 2-year-old brothers and sisters (18 boys, 18 girls). In the context of play, older siblings taught their younger siblings how to do everyday tasks such as washing and cooking. Ethnographic observations, discourse analyses, and quantification of discourse findings showed that children's teaching skills increased over the course of middle childhood. By the age of 4 years, children took responsibility for initiating teaching situations with their toddler siblings. By the age of 8 years, children were highly skilled in using talk combined with manual demonstrations, verbal feedback, explanations, and guiding the body of younger learners. Children's developing competence in teaching helped their younger siblings increase their participation in culturally important tasks.