Taliban authorities barred girls from secondary school in March 2022, after surging back to power in 2021 and imposing an austere vision of Islam with curbs the United Nations labels "gender apartheid".

On Wednesday morning, uniformed boys carried black and white Taliban flags as they lined the entrance of Kabul's Amani school, where local officials arrived for the ceremonial start of the school year.

But 18-year-old Kabul resident Zuhal Shirzad had to stay home when the school bell rang.

"Every year when my brother went to school, I felt very disappointed," she told AFP.

"I was happy for him and sad for myself," she said.

"This winter, my brother was studying and preparing for the university entrance exam," she added.

"I looked at him desperately and said that if I had been allowed to go to school, I would also be preparing for the university entrance exam now."

Afghanistan is the only country where girls' education has been banned after elementary school.

"None of the girls like me can continue our education and studies, and it is excruciating that boys can continue," said 18-year-old Asma Alkozai, from the western city of Herat.

"When there are barriers to education in society, such societies can never progress," she told AFP.

Online classes have sprung up in response to restrictions but a dearth of computers and internet, as well as the isolation of learning via screen, makes them a poor substitute for in-person learning, students and teachers say.

- Education 'essential' -

The education ministry announced the new school year on Tuesday, a day before the start of the Afghan calendar's new year, in a media invitation that expressly forbade women journalists from covering the ceremony at the Amani school.

At the ceremony, Taliban government Deputy Prime Minister Abdul Salam Hanafi praised education, saying, "A nation without education will always be dependent on others", local media reported.

Universities also recently started the new academic year, but women have been blocked from attending since December 2022.

Under the Taliban authorities, women have been excluded from many spheres of public life. Beauty salons have been shuttered and women have been barred from parks, funfairs and gyms.

Women's rights remain a key obstacle to international recognition of the Taliban government, which has not yet been recognised by any country.

The United Nations mission in Afghanistan (UNAMA) called on the authorities to "end this unjustifiable and damaging ban".

"Education for all is essential for peace & prosperity," the agency said in a post on social media platform X.

- 'Half of society' -

Taliban authorities have insisted since girls were barred from secondary school that they are working on establishing a system that aligns with their interpretation of Islamic law.

Thirteen-year-old Mudasir in eastern Khost province said girls and women should be given their rights to education "in the Islamic framework".

"They can go to school wearing Islamic hijab (covering)," he told AFP.

"They must be given their rights, because if a sister is educated, she can be the reason for the whole family to be educated."

Faiz Ahmad Nohmani, who started secondary school at a private institution in Herat on Wednesday, was excited to start the new academic year but said he was "very sorry" that girls were not also returning.

"Today, when I came to school, I wanted our sisters to come as well because they are half of society," the 15-year-old told AFP. "They should study like us."

Ali Ahmad Mohammadi, an 18-year-old student in his final year of secondary school, also in Herat, said he's aware of the chance he has to study.

"Literacy helps us progress, it saves society," said the teenager, who hopes to go on to university. "An illiterate society will always face stagnation."