Educational interventions are frequently designed to occur during early childhood, based on the idea that earlier intervention will have greater long-term academic benefits. However, surprisingly little is known about when cognitive and academic skills are most plastic, or malleable, during development. One way to study plasticity is to ask whether learning from targeted practice varies as a function of age. In this review, we summarize behavioral and neuroimaging studies that have tested for age-related differences in cognitive training gains, for executive functions, and for academic skills (reading and math). Findings are mixed, with no clear evidence for an overall younger age benefit. We discuss current challenges and opportunities for leveraging research on cognitive and brain plasticity to inform the timing and content of early academic interventions.