Click to expand Image A class at Wampewo Ntakke Secondary School in Kawempe tula village, Kampala, Uganda, November 4, 2024. © 2024 AP Photo/Hajarah Nalwadda A new United Nations Educational, Scientific, and Cultural Organization (UNESCO) report delivers a sobering message: the number of children out of school has risen for the seventh consecutive year, reaching 273 million worldwide.While nearly 90 percent of children globally complete primary school, the greatest gaps are in early learning and secondary education. Most out-of-school children—194 million—are of secondary school age, and roughly one-third of young people worldwide do not complete secondary school. At current rates, UNESCO estimates the world will not achieve 95 percent upper secondary completion until 2105.Children are also missing out on early childhood education. Only 60 percent of primary school students have had at least one year of pre-primary education; a critical stage when children’s brains are developing most rapidly. In sub-Saharan Africa, fewer than one in four children of pre-primary age are enrolled.For many of these children, cost remains the primary barrier to schooling. While primary education is nearly universally free, in line with international law, families are often required to pay for preschool and secondary schooling. In Uganda, for example, where there is no publicly funded preschool system, Human Rights Watch and the Initiative for Social and Economic Rights found that a majority of children miss out, because private preschool fees are prohibitively expensive for most families.These findings underscore the need for a new international treaty to guarantee free pre-primary and secondary education for all children. Under current international law, free education is explicitly guaranteed only at the primary level.Formal consideration of such a treaty, an optional protocol to the Convention on the Rights of the Child, began at the UN last year and more than 60 countries have already expressed support.A treaty will not bring every child into school overnight. But one that clearly guarantees free education can serve as a powerful catalyst for change, pressing governments to ensure that every child can attend school, regardless of their family’s ability to pay.When states reconvene in Geneva this August, they should seize the opportunity to close a longstanding gap in international law and open the door to a better future for millions of children.