Boys tend to start kindergarten less prepared, academically and behaviorally, than girls — and it can affect their achievement in the long term. To close the gap, one idea already in use by some parents is starting boys in kindergarten a year later — at age 6, with girls starting at age 5.

The practice is known by the sports term “redshirting,” or in education circles, giving children “the gift of time.”

Cutoff dates vary by location, but many schools require children to turn 5 by Sep. 1 of the year they start, so those born in the summer are about a year younger in class than those born in the fall. The children starting at age 6 are mostly the boys of rich white families born in the summer.

Some districts, including New York City, have banned this practice (with exceptions), in part because these children already tend to be ahead in school, so it could contribute to a long-existing achievement gap by race and family income.

But a different way to address that issue, supporters of redshirting say, is to make it the national policy for all boys. That would make it accessible to more Black and Hispanic boys and those from low-income families — the children least likely to be redshirted now but most likely to benefit, says Richard Reeves, president of the American Institute for Boys and Men.