Experts estimate school closures during the COVID-19 pandemic affected 95% of the global student population.

New research in the journal Nature Human Behavior underscores the need for policies and practices to address the resulting setbacks.

“It’s very hard to recover learning deficits once they are there,” said lead author Bastian Betthäuser of Sciences Po in Paris. “It really takes a huge amount of investment from a policy perspective and, of course, the necessary manpower in terms of qualified teacher personnel and opportunities for kids to learn outside of the normal school year.”

A meta-analysis of 42 studies across 15 countries finds schoolchildren lost about one-third of a year’s worth of learning and skills development during the pandemic — a loss they have yet to recoup.

“Government programs seem to have been successful in avoiding further learning deficits as the pandemic continued,” said Betthäuser. “But they did not succeed in recovering learning deficits that arose early in the pandemic.”

Researchers have pointed to possible contributing factors such as the effects of hybrid teaching, missed classes, loss of face-to-face instruction and mental and physical health problems related to economic insecurity.

Math delays were more pronounced than reading delays, and the existing gap faced by children from disadvantaged backgrounds widened.

“So the learning crisis is an equality crisis: Children from disadvantaged backgrounds were disproportionately affected by school closures, and at the same time, they have fewer means to continue learning from home, for example, with respect to a quiet place to study or a computer,” said Betthäuser.

He added that the problem didn’t wane just because the crisis fell off the front page.

“These learning deficits are still there. And we need continued investment from, from governments and schools,” he said.

Barring such action, the effects could harm this generation’s prospects in the job market.

“We know from the existing evidence in general that education is one of, if not the key predictor, for children's school-to-work transition, their success in the labor market, their success in building up their own livelihoods,” said Betthäuser. “So I think this is potentially going to be a real problem for this generation that experienced the pandemic in school.