"As the world faces unsustainable levels of inequality, we need education, the great equalizer, more than ever", he said in a video message, adding that "we must take bold steps now, to create inclusive, resilient, quality education systems fit for the future". Guterres warned the situation could lead to "a generational catastrophe that could waste untold human potential, undermine decades of progress, and exacerbate entrenched inequalities".
"Once local transmission of COVID-19 is under control, getting students back into schools and learning institutions as safely as possible must be a top priority", Guterres said.
What he's saying: "We are at a defining moment for the world's children and young people", Guterres said. "And only a quarter of secondary school children in developing countries were leaving school with basic skills".
Guterres said that as of mid-July schools were closed in some 160 countries, affecting more than 1 billion students, while at least 40 million children have missed out on pre-school.
She said a coalition of global organizations launched a campaign Tuesday called "Save Our Future" to amplify the voices of children and young people and urge governments worldwide to recognize that investing in education is critical to COVID-19 recovery and to the future of the world.
Reopening schools should be the "top priority" as coronavirus lockdowns ease with a billion children left facing a "generational catastrophe" after classrooms closed, the head of the United Nations has warned.
Germany was the first European country to reopen schools this week as the summer holidays are coming to an end in several states.
In the United States, pupils are also starting a new year and President Donald Trump has urged schools to reopen despite an uptick in COVID-19 cases in several parts of the country.
The new coronavirus has infected more than 18 million people worldwide and killed at least 692,000, according to data collected by the Johns Hopkins University.