This study evaluated the impact of a theory-driven cognitive attention training program, "Keeping Score!," in improving students' sustained attention capacity. Training was based on sustained updating. Students engaged this process by mentally keeping score during an interactive game of table tennis without external aids. Students (9-11 years) were assigned to a 6-week training program (n = 18) or an active control (n = 18). Assessments of sustained attention/working memory and parent ratings of executive function were completed at pretraining, post-training, and 6-week follow-up. We found no evidence to support the efficacy of training (i.e., there was no statistically significant time × group interaction effects for any outcome). Overall, these findings add to the mixed body of literature supporting the efficacy of cognitive attention training for improving children's attentional capacity. One possibility for why the training program was unsuccessful is perhaps that cognitive attention training may not be sufficient for enhancing sustained attention.