Even with all the rising measures of mayhem in Afghanistan’s long war — civilian casualties, suicide bombings and refugees, to name a few — the number of children out of school had been falling. Until now.

A study released Monday by Unicef shows that Afghanistan’s out-of-school population has risen to 3.7 million, or 44 percent of the school-age population, compared with 3.5 million, or 40 percent of the school-age population, a few years ago.

It was the first time the number of out-of-school children in Afghanistan had risen since the ouster of the Taliban government by the American-led invasion in 2001. Under the Taliban, many schools were closed and girls were barred from attending.

The resumption of the provision of basic education in Afghanistan and the inclusion of girls have been regarded as a relative success story in the country.