School closures during the pandemic have set back children's learning in many G20 countries and could have a long-lasting negative impact on GDP in advanced economies, the IMF said Tuesday.

Recent assessments of schoolchildren show that widespread virtual learning during the Covid-19 pandemic resulted in lower academic levels in India, Germany, the United Kingdom, Brazil and the United States, where many institutions were closed for more than a year.

"If these learning losses aren't addressed, affected students could experience a lifetime of depressed earnings," the Washington-based crisis lender said in a report.

IMF economists observed that current students will make up nearly 40 percent of the working-age population in G20 economies for decades to come.

"While much is still unknown, our simulations show that, once all such students are in the labor market, gross domestic product for advanced G20 economies could be as much as three percent lower in the long run," the report warned.

Poorest households suffered the worst learning losses, and their prospects stand to be "particularly diminished, further widening income inequality," the IMF said, according to AFP.

If learning loss from the pandemic goes unaddressed, it could result in lifetime income losses of 1.5 to 10 percent for residents of G20 nations, the IMF estimates.