Daesh has seized land in Syria and Iraq and imposed its strict version of Islamic law.
In November, it shut schools in areas it controls in eastern Syria pending a religious revision of the curriculum.
The group stands accused of massacres, sexually enslaving women and girls and recruiting children as fighters.
“In December there was a decree of [Daesh] ordering the stoppage of education in areas under its control,” Unicef spokesman Christophe Boulierac said.
“Daesh said that the curriculum needed to be reshaped or re-conceived.” Children enrolled in primary and secondary schools in Raqqa, and rural areas of Deir Al Zor and Aleppo provinces are affected by the closures, he said. Teachers must undergo retraining.
Unicef also said that at least 160 children were killed and 343 wounded in attacks on schools across Syria last year. The toll was probably an underestimate due to difficulties of access and obtaining data generally, Boulierac said.
“In addition to lack of school access, attacks on schools, teachers and students are further horrific reminders of the terrible price Syria’s children are paying in a crisis approaching its fifth year,” Hanaa Singer, Unicef representative in Syria, said in a statement.
Daesh has been the target of US-led air strikes in both Syria and Iraq since September.