This paper reports on a study that was conducted on the effects of training students in specific strategic and meta-cognitive questioning strategies on the development of reasoning, problem-solving, and learning during cooperative inquiry-based science activities. The study was conducted in 18 sixth grade classrooms and involved 35 groups of students in three conditions: the cognitive questioning condition; the Philosophy for Children condition; and the comparison condition. The students were videotaped as they worked on a specific inquiry-science task once each term for two consecutive school terms. The results show that the students in all conditions demonstrated more helping discourses or discourses known to mediate learning than any other of the discourse categories. This outcome is encouraging because it is the helping discourses where students provide explanations, elaborations, and reasons that promote follow-up learning. (Contains 1 table.)