24 8and 9-year-old children of each sex and at low and high levels of anxiety as measured by the Test Anxiety Scale for Children (N = 96) were divided equally into 6 experimental groups according to the type of pretraining (success, failure, or no pretraining experience) and reinforcement condition (social reinforcement or nonreinforcement from 1 of 2 males) in a subsequent angle-matching task. The Ss' achievement expectations were assessed prior to and following the experimental task. Major results were: (a) Following social reinforcement, expectations increased, the effect being stronger for girls than boys. (b) Following nonreinforcement, achievement expectations remained stable for both sexes. (c) Initial achievement expectations correlated negatively with test anxiety for girls. (d) Change in achievement expectation correlated positively with test anxiety for boys in the social reinforcement condition. The sex difference in the facilitating effects of social reinforcement on achievement expectations was considered as being part of a possible Sex of S by Sex of E interaction. It is suggested that sex differences in learning and cognition may be greater than has been recognized. Theorizing on the causes of the negative relation between a high level of test anxiety and children's achievement behaviors and intellectual