Schooling may shape children's abilities to control their attention, but it is unclear if this impact extends from control over visual objects to encompass multisensory objects, which are more typical of everyday environments. We compared children across three primary school grades (Swiss first, third, and fifth grades) on their performance on a game-like audiovisual attentional control task, while recording their electroencephalogram (EEG). Behavioral markers of "visual" attentional control were present from third grade (after 2 years of schooling), whereas multisensory attentional control was not detected in any group. However, multivariate whole-brain EEG analyses ("electrical neuroimaging") revealed stable patterns of brain activity that indexed both types of attentional control--visual control in all age groups, and multisensory attentional control from third grade onward. Multivariate EEG approaches can uncover otherwise undetectable mechanisms of attentional control over visual and multisensory objects, and characterize how these mechanisms differ across educational stages.