In addition, about 770 million adults are illiterate, most of them women, Deputy Secretary-General Amina Mohammed told the U.N. General Assembly on the International Day of Education.

She said the situation is "alarming," not only because of the millions who aren't getting an education — and never did — but also "because of the crisis in the number of children, young people and adults who are in education, but not learning."

Former British prime minister Gordon Brown, the U.N. special envoy for education, has said he continues to be "shocked" that more than 400 million children leave school for good at age 11 or 12 and "800 million children are leaving the education system without any qualifications worth their name."

The U.N. goal for 2030 is to "ensure inclusive and quality education for all and promote lifelong learning."

At an event at the U.N. Educational, Scientific and Cultural Organization in Paris, UNESCO Director-General Audrey Azoulay said "not only do we need massive investment, but an overhaul of educational systems is necessary."

To rethink education and prepare the coming generation to deal with major issues like the digital revolution and the climate emergency, Azoulay said UNESCO appointed a commission of independent experts last September led by Ethiopia's President Sahle-Work Zewde to produce a report in November 2021 on the Futures of Education.

Brown said one reason why the situation is "so grave" today is that there are 75 million children in crisis-affected countries who are unable to go to school, have their education disrupted, and don't attain any educational standards.

Yasmine Sherif, director of Education Can't Wait which is the first global fund dedicated to education in emergencies, told a news conference at the U.N.: "Just think what will happen with this generation, and with all of us one day, if these 75 million children don't access a proper, decent quality and continued education," she said.

The fund has received pledges of almost $590 million since it began three years ago and is helping youngsters in 30 conflict and crisis-affected countries from Syria and Afghanistan and Mali, Bangladesh and Central African Republic, she said.

Brown, who chairs the fund's high-level steering group, said it is crucial for all levels of education. He said only a fraction of refugees — 1-3 percent — go on to higher education. compared, for example, with Syria where it was 20 percent before the conflict began in 2011.

General Assembly President Tijjani Muhammad-Bande told the U.N. event that "there has been an increase in school enrollment rates worldwide, with more children going to, and staying in school longer.

"While this is commendable," he said, "it is unacceptable that 20 years into the 21st century about 258 million children and youth do not attend school, 617 million children and adolescents cannot read and do basic math and millions of refugees and internally displaced persons, and people with disabilities are out of school," he said.

Muhammad-Bande called this "a blight" and urged governments to ensure access "to free and quality primary and secondary education, as well as affordable and inclusive vocational and technical education."

Deputy Secretary-General Mohammed said: "This international day must be a call to action ... so that quality education for all is no longer a goal for tomorrow, but a reality."