In his 1952 novel, Invisible Man, the late Ralph Ellison famously portrayed American blacks as silent, long-suffering, and entirely unnoticed by the majority white population. In 2016, there is a new – and global – invisible class: the 260 million boys and girls who are currently denied access to basic education.

Today’s invisible victims are refugee children holed up in tents, shacks, and hovels who will never enjoy a first day at school; they are the millions of 9 to 12-year-olds condemned to child labor, and the millions of young girls destined for child marriage and denied an education simply because of their gender. Ensuring a better future for these children is the civil-rights struggle of our time.

Out-of-school children are losing out because of our failure to invest in education; but so, too, are another 600 million boys and girls who are in school, but not learning. In low- and middle-income countries, half of all primary-school-age children don’t learn basic literacy and numeracy skills.

Read more from UN Special Envoy for Education and Commission Chair, Gordon Brown, on Project Syndicate.