Governments are struggling to meet the rising demand for secondary education, especially in sub-Saharan Africa, where there are enough school places for just 36% of children of age to enrol, according the latest edition of the Global Education Digest, published by the Unesco Institute for Statistics.

Globally, secondary schools have been accommodating almost 100-million more students each decade, with the total number growing by 60% between 1990 and 2009. But the supply is dwarfed by demand as more countries approach universal primary education.

In 2009, 88% of children enrolled in primary school reached the last grade of this level of education, compared to 81%. Yet, in 20 countries – mostly in sub-Saharan Africa – a child in the last grade of primary school has a 75% chance at best of making the transition to lower secondary school.