It is suggested that dependent teacher-child relationships are associated with emotional insecurity and a lack of autonomous exploration that interferes with children's school development. This might be especially observed among children with attachment problems who may have developed a profound sense of insecurity in relationships with others. In this study, the effects of dependency on children's classroom and peer engagement were examined as well as the protective role of teacher sensitivity. The sample included 85 Belgian children with mild to severe attachment problems and 70 teachers from special education schools. Data on teacher sensitivity and teacher-child relationship quality (dependency, conflict, closeness) were collected in the first trimester of the school year using independent observations and teacher questionnaires respectively. Teachers also completed questionnaires on classroom engagement (independent classroom participation) and peer engagement (social withdrawal) in the first, second, and third trimester. Dependency was uniquely associated with lower levels of independent classroom participation. Moreover, low teacher sensitivity predicted declines in independent classroom participation among overly dependent children, whereas high teacher sensitivity predicted growth in independent classroom participation. Dependency and teacher sensitivity did not predict social withdrawal. This study highlights the importance of teachers being sensitive to the needs of overly dependent children to support the autonomous exploratory behavior of these children.