A partner’s competence should logically favor cooperative learning. However, research in cooperative learning has shown that a partner’s competence may or may not activate a threatening social comparison and yields dual effects: It is beneficial when students work on complementary information while it is detrimental when students work on identical information. Two studies conducted at elementary school (study 1 with 24 fourth graders working on encyclopedic texts, and study 2 with 28 fifth graders working on argumentative texts) replicated that interaction: Information distribution (complementary vs. identical information) moderated the relationship between partner’s competence and pupils’ learning outcomes. The relation between partner’s competence and students’ performances was positive when working on complementary information, but negative when working on identical information. A third study confirmed that working on identical information led to a competitive social comparison whereas complementary information reinforced the pupils’ cooperation perception. Contributions to cooperative learning research are discussed in terms of the competitive comparisons that may arise during cooperative learning at elementary school.