Two-thirds of girls in Afghanistan are not in school, a new report by Human Rights Watch (HRW) has revealed.

16 years after a US-led military intervention ousted the Taliban, the majority of Afghan girls are still not receiving a proper education. After the Taliban regime ended, millions of girls attended school for the first time, but in recent years progress on girls' education has stalled.

Almost 85% of the 3.5 million Afghan children out of school are girls and only 37% of teenage girls are literate, compared with 66% of teenage boys, according to HRW. Only 25% of university students are women.

The human rights organisation warned that the real situation is likely even worse than the statistics suggest as Afghanistan does not record children being out of school until they have stopped attending class for three years.

There are numerous factors restricting girls from accessing education in Afghanistan. Mounting insecurity, poverty and displacement are driving many girls out of school, according to Liesl Gerntholtz, HRW women's director.

Another barrier is the lack of schools and teachers available to teach girls. Many families will not allow their teenage daughters to be taught by a man, but in half the country's provinces fewer than 20% of teachers are female. In large parts of the country, girls are prevented from going to school because of a lack of proper toilet facilities.

A third of Afghan girls are married before the age of 18 and forced to drop out of education after becoming engaged, the report stated.

Education is compulsory for all children until the age of 14, but HRW found that many girls dropped out before and spent their childhood weaving, begging or picking up garbage instead of studying.

Heather Barr, who wrote the HRW report, told IBTimes UK that progress made towards getting girls into education has stalled in recent years due to insecurity in Afghanistan.

The Taliban and other insurgents control around 40% of the country's districts and have driven thousands of Afghans from their homes as they continue to wage war with government forces. In many Taliban controlled areas, girls are banned from attending school altogether. Girls who do venture away from their home face numerous threats including acid attacks, kidnapping and sexual harassment.

Barr said that getting girls to go to school is not a priority for the government and its donors. "Hiring of teachers and construction of schools has largely stopped, and donors are disengaging from Afghanistan," she said.

She described the long-term consequences of girls missing out on education as "devastating", not just for them, but for "the country as a whole."

"Girls who are out of school are at higher risk of child marriage. The children of uneducated mothers have worse health outcomes. The country's economy will never prosper if half the workforce is illiterate," Barr said.