Two measures were used to investigate the socioemotional effects of collaborative philosophical enquiry on children aged 11 at pre-test in five experimental and three control primary (elementary) school mainstream classes. Experimental teachers received initial and follow-up professional development. In a pre-post controlled design, experimental pupils used collaborative enquiry for one hour each week over a seven-month inter-test period. Control pupils followed a normal curriculum. On a test of self-esteem as a learner, experimental pupils (n = 119) gained significantly while controls (n = 52) did not. There was evidence of significant reduction in dependency and anxiety and of greater self-confidence. Girls tended to gain more than boys. These results were fairly consistent across schools/classes. On a scale for teacher observation of pupil social skills in problematic situations, a random sample of experimental pupils (n = 25) gained no more than controls (n = 22) overall. However, these results showed considerable variation across schools/classes. Implications for future research, practice and policy are addressed. (Contains 4 tables.)