The study says the disruption to lessons will have a negative impact on the future skills of the workforce.
The research group, including academics from Cambridge and Bristol universities, says it will cost billions in a reduced growth rate.
Getting pupils back to school must be a priority, says the study.
The report is from an inter-disciplinary group of experts, convened by the Royal Society to measure the long-term impact of the Covid-19 pandemic.
It says there is a “huge base of evidence” showing that earnings are linked to education and skills – and that losing so much time in school will have negative economic consequences.
“Around a quarter of the entire workforce will have lower skills, with a consequently lower growth rate,” says the research.
Evidence of long-term damage from reduced schooling included studies in Argentina, where year groups affected by prolonged strikes were found to have reduced average earnings into mid-life, of 1.9% for women and 3.2% for men.
The researchers call for the safe return to school to be a top priority and for clear plans to minimise the risk of any further disruptions.
“We know how damaging it is for children to miss out on school,” said Simon Burgess, professor of economics at the University of Bristol.
This damage will not be evenly spread from the pandemic, says the study, with those already disadvantaged likely to be among those who have missed out most from trying to study at home, rather than face-to-face in the classroom.
“Children from low-income households in particular are more likely to lack the resources – space, equipment, home support – to engage fully with remote learning,” said Anna Vignoles, professor of education at the University of Cambridge.