This was despite online learning having a potential to reach more than one billion students, the study by the UN's education agency (Unesco) said.

However, it did curb a crisis in the education sector when schools closed in 2020 because of coronavirus, its report on technology in education said.

Distance learning also helped 22,000 children affected by the Islamist Boko Haram insurgency in north-eastern Nigeria.

Mobile phones and radios were used to support them, showing an improvement in both literacy and numeracy skills.

But the report noted that access to internet was still unequal: “Globally, only 40% of primary, 50% of lower secondary and 65% of upper secondary schools are connected to the internet.”

The report advises countries to have technology designed on their own terms so that in-person, teacher-led instruction is not lost.

Unesco also warned that online learning was not a substitute for human interaction, saying the use of technology by students both at home and in classrooms could be “distracting, disrupting learning”.

“Its use must be for enhanced learning experiences and for the well-being of students and teachers, not to their detriment," Unesco head Audrey Azoulay said.