The UN chief called a special summit on education a day before world leaders meet Tuesday for the annual General Assembly, although a number of key officials including US President Joe Biden delayed their arrivals in New York due to Queen Elizabeth II's funeral.
"Education is in a deep crisis. Instead of being the great enabler, education is fast becoming the great divide," Guterres told the summit.
He warned that the Covid-19 pandemic has had a "devastating impact" on learning, with poor students lacking technology at a particular disadvantage, and conflicts further disrupting schools.
Guterres appealed to all countries to prioritize increasing spending per student even amid question marks over the global economy.
In a report earlier this month, the UN Development Program said Covid has set back humanity's progress by five years.
Guterres also called out Afghanistan's Taliban, who have deprived more than one million teenage girls of education since the Islamist militants returned to power in August 2021.
"I appeal to the authorities in Afghanistan: Lift all restrictions on girls' access to secondary education immediately," he said.
Addressing the summit, Somaya Faruqi, who was part of Afghanistan's celebrated girl's robotics team, said the Taliban are "slowly erasing our existence in society."
"Thousands of girls may never return back to school. Many have been married off. The promises of reopening schools came and went," she said.
Appealing to world leaders, she said, "You must not forget those who are left behind, those not lucky enough to be at school."
"Show your solidarity with me and millions of Afghan girls."