This cross-sectional study aimed to investigate developmental changes in the efficiency of sustained, selective, and divided attention in a group of children aged 6-12 years by means of a computerized test battery. Participants included 199 children (51% female, majority White) who had normal or corrected-to-normal vision and no history of either neurological or attention deficit disorders. The study was conducted in three different schools. We used a convenience sampling strategy; each age group was sampled from one of the schools and was represented by students selected from different (parallel) classes of the same grade level. The three aspects of attention showed different developmental trajectories from 6 to 12 years. In terms of accuracy, selective attention was found to improve gradually, while the efficiency of divided attention increased dramatically across the school-age years. In terms of reaction time, all attentional components showed a slow developmental time course. The results indicate that situations in which children have to divide attention among several sources of visual information while looking for two target stimuli considerably hamper their task performance. This is especially true for children of senior preschool and primary school age.