The U.N. children's agency says more than half of South Sudanese children are not in school, the highest proportion of children out of class in any country.

UNICEF said in a statement Tuesday that 51 percent of children between ages 6 and 15 are not in school in South Sudan, which has seen violence for two years as government forces battle rebels.

Over 800 schools were demolished in fighting that forced over 400,000 children out of classrooms, while 1.4 million children were already missing class before the conflict began. South Sudan is followed by Niger, where 47 percent of the children are not in school, according to UNICEF.

South Sudan's government and the rebels signed a peace agreement in August, although violence persists in some areas.