Not nearly, says Laurence Steinberg, a world-leading expert in adolescent brains. He insists there’s much more that schools – and parents – should be doing to help young people build the best possible brains.

“Adolescence is our last best chance to make a difference,” the Temple University psychology professor says in his 2014 book Age of Opportunity.

Citing neurological research that has largely emerged over the past five years, he says adolescence is a second window – after the first three years of life – during which the brain is exquisitely sensitive to experience. In other words, it is remarkably plastic.

Steinberg has spent 40 years ­studying adolescents and their brains. He has more than 350 academic articles a...