The Taliban have allowed middle- and high-school girls to resume studies in several provinces of northern Afghanistan, in an indication of how the Islamist group’s policies on key issues are being influenced by cultural differences within the country.

In September, the Taliban reopened secondary schools for male students across Afghanistan but said nothing about their female peers. That amounted to a de facto ban on girls going to school after sixth grade. Elementary schools have reopened for all, with boys and girls being...

The Taliban have allowed middle- and high-school girls to resume studies in several provinces of northern Afghanistan, in an indication of how the Islamist group’s policies on key issues are being influenced by cultural differences within the country.

In September, the Taliban reopened secondary schools for male students across Afghanistan but said nothing about their female peers. That amounted to a de facto ban on girls going to school after sixth grade. Elementary schools have reopened for all, with boys and girls being taught separately.

But in four northern Afghan provinces—where women traditionally have had more active roles in society than in the more conservative south and east—secondary schools for girls have reopened, too, with the approval of local Taliban government officials. The decision, which hasn’t been widely publicized, was confirmed by teachers, students and a Taliban spokesman.

The move indicates a degree of willingness from the Taliban to shape policy around cultural differences across Afghanistan, unlike in the 1990s, when they imposed harsh social rules on everyone under their rule.

In the provinces of Balkh and Kunduz, which include the north’s two biggest cities of Mazar-e-Sharif and Kunduz, schools for teenage girls have been open for around a month. Top provincial Taliban officials have met with school principals there and ordered them to get girls to return to school, according to people who attended the meetings or were briefed about them.

Shamayel Sovaida, the principal of Fatima Balkhi High School in Mazar-e-Sharif, welcomed the decision: “We and our students are very happy that girls’ schools have reopened and that girls can continue their lessons.”

In Balkh, the top Taliban education official asked teachers to persuade girls to return to school. “Those female students who are not coming to the classes, go and knock on their door, and tell them to come to school,” the official said, according to a local teacher briefed about the meeting.

Schools for teenage girls have also reopened in the provinces of Sar-e-Pul and Jawzjan, with Taliban representatives often visiting them.

“The Taliban come to school and check the student attendance register. If a teacher is sick, the Taliban just mark her absence,” said Sadaf, a 10th-grade student in Sar-e-Pul. “They tell us to come to school wearing an Islamic hijab, to not wear high heels or sandals, and to not make a sound while walking.”

Even where schools have reopened, not all female students have returned to class. In one school in the northern city of Kunduz, a third of the 3,000 students are absent, according to its principal. Many families have fled the city. Others don’t trust assurances from local Taliban that girls are allowed to go to school. Some worry that Taliban fighters will harass their teenage daughters on their way to school.

The Taliban’s decision to severely restrict education for girls after taking power has been one of the most tangible signs that the hard-fought rights of Afghan women are being rolled back. How the new Kabul government treats women is a major marker of whether the Taliban have become more moderate—and acceptable to the international community—since deposing the Afghan republic Aug. 15.

In the late 1990s, the Taliban imposed harsh restrictions on Afghan women, banning them from education and work, and prohibiting them from leaving home without a male guardian.

Akif Muhajer, the spokesman for the Taliban’s Ministry of Suppressing Vice and Promoting Virtue, which is tasked with enforcing religious compliance, confirmed in an interview that high schools for girls were open in four northern provinces. He added that such reopenings “will proceed throughout the country.”

A spokesman for the Ministry of Education didn’t reply to a request for comment.

It is unclear how soon—or if at all—high schools for girls will reopen nationwide. The Taliban leadership in Kabul has so far avoided taking a clear position on female education, with officials saying a committee of Islamic scholars must examine the issue first.

When asked about girls being excluded from school, Amir Khan Muttaqi, the Taliban foreign minister, on Monday said the obstacle was partly cultural. “In Afghanistan, one thing is what Afghans want. Another thing is what the international community wants,” he said during a public event in Doha, Qatar.

Northern Afghanistan is populated mostly by the Tajik, Hazara and Uzbek communities, where attitudes to women are more liberal than in the rural Pashtun heartland of southern Afghanistan, the Taliban’s cradle and traditional stronghold.

Shukria Hesarnaye, a teacher in the southern Helmand province, said she has been waiting for weeks for an answer from the Taliban’s local education officer on whether high schools for girls could reopen.

“He did not give me a hopeful answer. He just told me, ‘We are waiting for a plan,’” said Ms. Hesarnaye. “How is it possible that schools are open in the north but not in the south? If there is a law, it should be implemented in every corner of the country. Every official is making decisions on his own in his province.”

In Afghanistan’s more culturally conservative south and east there is more political resistance within the Taliban’s ranks to allowing girls to go to school—and less pressure from the population to make it happen, said Pashtana Durrani, an Afghan education activist who is originally from the southern province of Kandahar.

“It’s a decision that is supposed to be taken by the leadership but instead it’s been taken in provinces. It’s like a federal system,” said Ms. Durrani. “There is a sense that they are taking the decision [to open girls’ schools] in places where they won’t face challenges. And in the south they are facing more challenges. The Taliban in Kandahar are much more conservative. They see schools as infidel projects.”

Ms. Durrani decided to take the matter into her own hands: Through her education charity, called Learn, she set up a secret school for teenage girls. Around 100 girls between the ages of 13 and 18 are enrolled at the school, which has been operating for around 10 days in an undisclosed location. She hopes it will be temporary.

Ms. Durrani expects international pressure—and the promise of humanitarian aid—will eventually force the Taliban to reopen high schools for girls in all provinces. “They have to do something. If not for legitimacy, then for the money,” she said.

It is unclear how long even the girls’ schools that are functioning now will be able to stay open: Most teachers, like other government employees, haven’t received a salary in months.

The Taliban government is broke. Over 70% of the previous government’s nonmilitary budget came from international aid, which has been mostly suspended. More than $9 billion of the central bank’s assets are frozen in the U.S. and other Western nations. The banking system is barely functioning. Revenue raised through customs and taxation can only cover a fraction of public expenditures.

Teachers in northern Afghanistan say that while they are happy that their female students can go back to school, their own financial situation is unsustainable. Some can’t even afford the cost of the commute from their homes to school.

“We are working as volunteers these days. We haven’t been paid in three months,” said Shamim Sayal Jamshid, the principal of Sedarak Girls High School in the city of Kunduz. “But we are happy that the doors of schools are open for girls.”

—Jalaludin Nazari and Saeed Shah contributed to this article.

Write to Ehsanullah Amiri at Ehsanullah.Amiri@wsj.com and Margherita Stancati at margherita.stancati@wsj.com