Most schools for girls over sixth-grade have been shut since the Taliban takeover of Afghanistan in August. The group had previously said all teenage girls would be allowed to return to classes from March 23, the start of the new school year.

But late Tuesday, the Taliban’s Ministry of Education instructed secondary schools for girls to stay shut until further notice. Girls’ schools would reopen only once uniforms had been designed in accordance with Islamic law and tradition, the ministry said.

In an interview, a ministry representative, Waheedullah Hashimi, said a date hadn’t been set to reopen secondary schools to girls.

The international community has put pressure on the Taliban to respect women’s rights, starting by reopening all schools for girls. Keen for their government to be recognized as legitimate, the Taliban have long said that, in principle, they are in favor of education for teenage girls, as long as appropriate gender segregation arrangements are made.

But education for women remains a divisive issue for the Taliban. When they first came to power in the 1990s, they banned all education for girls, including primary school, and barred women from almost all professions.

Many Taliban remain hostile to the idea that women and girls should receive an education, or play active roles in public life. The Taliban leadership is also aware that softening their policy on women could push their hard-line members to defect to Islamic State’s regional offshoot. Islamic State and the Taliban consider each other enemies.

Teachers, parents and hundreds of thousands of students who had been preparing to return to school were caught off guard by the late-night announcement. On Wednesday morning, many girls put on their uniforms and went to school—only to discover they had to go back home.

“I thought life would return to normal again this spring, with girls going back to school and pursuing their dreams, but the catastrophe continues,” said Somaya, 25, a high-school teacher from Kabul who didn’t want her full name used. “With this announcement, I feel just like I did when the Taliban entered the city for the first time: desperate, angry, insecure. The Taliban haven’t changed. Their attitude toward women is always the same.”

International condemnation was swift. The United Nations mission in Afghanistan said it deplored the decision to extend the ban on teenage girls attending school.

The U.S. chargé d’affaires for Afghanistan, Ian McCary, said he was deeply troubled by the news. “This is very disappointing and contradicts many Taliban assurances and statements,” he said.

Despite hearing that schools would remain closed, Zainab Maqsudi, an eighth-grade student, went to her school in western Kabul on Wednesday morning hoping it would be open. She joined a large group of girls who were waiting outside the main gate.

“We were not allowed to enter. The Taliban started firing in the air. I ran away, I got scared. All girls dispersed and fled the area,” said the 14-year-old. “I’m so sad they didn’t allow me to go to school. They are playing with my future.”

Getting an education has been especially difficult for Ms. Maqsudi, even before the Taliban captured Afghanistan. In May last year, suspected Islamic State militants stormed her school in western Kabul. She was injured in that attack, which still gives her nightmares.

“I appeal to the Islamic Emirate to allow us to study for the sake of progress and for our country,” she said. The Taliban refer to their government as the Islamic Emirate.

Upon hearing the news, a schoolgirl in Kabul broke down in tears on live television. “What is there to say? What can we do? We are girls, we are from Afghanistan. But we are also human beings. Why can we not go to school?” she told a reporter for Afghanistan’s Tolo News television channel. “How long must this go on for? It’s already been 186 days.”

Elsewhere in Kabul, a group of female students in black and white uniforms staged a protest against their school’s continued closure, Afghan television showed. Another group of schoolgirls, concealing their faces, released a video of themselves holding up signs decrying the school ban.

“Hijab is an excuse. Misogyny is the plan,” read one of the signs, referring to the Islamic head covering. “Education is my right,” read another.

In September, the new Taliban government ordered secondary schools for boys to reopen, but said nothing about girls. That was tantamount to ordering middle and high schools for girls to stay shut.

The Taliban’s mixed attitude to education for women is reflected in their policies. Primary schools reopened for girls in September, and women returned to university classes last month.

Since September, the Taliban has allowed some secondary schools to reopen to girls in a few provinces. Those provinces are mostly in the north, where attitudes toward women are generally more liberal than in the rural south, the Taliban’s traditional stronghold.

In one of those provinces, Balkh, the Taliban introduced rigid gender segregation after schools reopened in the fall.

“The changes are enormous,” said a female teacher from the city of Mazar-e-Sharif, who didn’t want to be named. “We cannot sit with our male colleagues in one office. Our school principal is a man. We are not allowed to go see him to resolve our issues.”

—Zamir Saar and Jalal Nazari contributed to this article.