Kindergarten is where 5- and 6-year-olds learn the building blocks of how to be students, skills such as taking turns and working together that they will need for the next 12 years of formal schooling. It coincides with a critical window for brain development, the time between 5 and 7 years old when neural connections are firing most rapidly for higher-cognitive functions like problem-solving and reasoning. Kindergarten “can’t be replicated even by the very best teachers in the virtual environment,” said Whitney Oakley, chief academic officer for North Carolina’s Guilford County Schools. A missed, delayed or low-quality kindergarten experience “could impact this generation of kids for their lifetime.” The most reliable predictor of positive outcomes in adulthood, from educational attainment to mental health, isn’t academic ability but how well students cooperate with peers, help others, understand feelings and resolve conflicts, according to a 2015 study by Mark Greenberg, a professor of developmental psychology at Penn State University, that tracked 750 people from kindergarten to about 25 years of age.