The failure of poor nations to prioritise education will weaken economic growth and undermine efforts to meet poverty targets, former prime minister Gordon Brown said on Friday.
Brown was speaking at the launch of "Education for all", a report that calls for the creation of a global fund on education to help governments get children into school.
It will be presented to political leaders at the G8 summit in France next week.
It was a "scandal" that some 70 million children were still not getting to attend school despite pledges made by global leaders to provide funds to make education accessible to poor children, Brown said.
"In the next four years we must make a commitment to train a million teachers. Pledges have to be honoured," he added.
Brown heads the High Level Panel on Education, part of the Global Campaign for Education, a grouping of campaign groups pressing governments for better schools. Graca Machel, the wife of Nelson Mandela, is another panel member.
The report said sub-Saharan Africa faced the biggest regional challenge, with 10 million children forced to drop out of primary school every year.
"For households living with poverty, external shocks such as drought, natural disasters, unemployment or rising food costs may results in children being forced into employment," the report said.
Brown said the world was slipping backwards from an international commitment made in 2000 to get all of the world's children into decent quality education by 2015.
In Malawi, more than half of children tested in English at the beginning of grade four could not read a single word, the report said