Experiment 1: Hierarchical linear modeling of growth trajectories of three executive functions (inhibition; rapid automatic switching, RAS; and combined inhibition/switching) in typical readers and writers showed steady improvement of inhibition but leveling of RAS and inhibition/switching about fourth grade. In multiple regressions, RAS, entered after inhibition, contributed uniquely to literacy outcomes at every grade. Improvement of executive functions over the first four grades predicted literacy outcomes at fourth grade. Experiment 2: For children with dyslexia, executive functions explained less variance in literacy outcomes, and boys were worse in inhibition and inhibition/switching. Developmental, educational, and clinical significance of findings are discussed.