The present study builds on research that indicates that teachers play a key role in promoting those interactional behaviours that challenge children's thinking and scaffold their learning. It does this by seeking to determine whether teachers who implement cooperative learning and receive training in explicit strategic questioning strategies demonstrate more verbal behaviours that mediate children's learning than teachers who implement cooperative learning only. The study also sought to determine whether students who receive training in explicit questioning strategies demonstrate more explanatory behaviour than their untrained peers, and, as a consequence, do these same students demonstrate more advanced reasoning and problem-solving skills on follow-up reasoning and problem-solving tasks. The study involved 31 teachers in two conditions, the cooperative + strategic questioning condition and the cooperative condition, and two groups of students from each teacher's classroom. The results show that the teachers in the cooperative + strategic questioning condition used significantly more mediating behaviours than their peers in the cooperative condition. The study also showed that the children in these teachers' classes engaged in more elaboration and obtained significantly higher scores on the follow-up reasoning and problem-solving tasks. The study demonstrates the importance of explicitly teaching strategic questioning strategies to children during cooperative learning.