Madrassas in Pakistan have been under close scrutiny since the London bombings on 7 July, with President Pervez Musharraf saying all foreign students must leave despite the schools' protestation that they have nothing to do with terrorism.
The Jamia Binoria madrassa houses 5,000 students
It's the last week of term at the Jamia Binoria madrassa in Karachi and everyone is busy with lessons.
From the outside the religious school is indistinguishable from the textile factories that surround it in this industrial area.
But once past the steel gate and the guards armed with shotguns, visitors enters a shady, open-air courtyard.
The quiet is broken only by the distant, raised voices of the teachers as they address their classes of 100 or more students.
Jamia Binoria is home to 5,000 students - most are boarders, eating and sleeping on the premises.
Lessons are Islamic law and history, science and English.
Five hundred are girls and young women. They are taught in a strictly segregated section.
But what marks out this madrassa is its foreign students.
The government has estimated there are 1,400 foreigners studying religion in Pakistan.
At least 100 of them are at Jamia Binoria.
Some have been here for years, studying for the equivalent of university degrees.
Others are short-term visitors, often from the South Asian diaspora, sent here by parents to learn about their culture and Islam.
All will have to leave when the ban on foreign students is enforced.
Abdus Samad Juber's family is originally from Bangladesh.
But he speaks with a London twang. He was born and spent all his life in Crawley, south of the British capital.
He is in the third year of a six-year course, but thinks he will probably have to abandon it.
"Of course I don't think it's fair, it's ridiculous," he says of the government decision.
"Although a minute number of people may be involved in illegal acts or terrorism or fundamentalism, to say all foreigners get out of the country is silly and ridiculous."
He shares his room with two Americans. They are in what they admit is the VIP suite of the madrassa - a cool room where the air conditioning runs 24 hours a day and there is a computer hooked up to broadband.
Afzal Sheikh Junior and Farhan Mughul, from New York, both wear long robes, skull caps and full beards.
"They're saying, 'oh there's jihad training'," says Afzal Sheikh Junior. "I've been here and I haven't seen anything like that."
Mufti Mohammed Naeem is in charge of Jamia Binoria and founded the community 25 years ago.
After the attacks on London's transport system on 7 July there were unconfirmed reports one of the bombers may have visited a madrassa.
Mufti Naeem was keen for me to look around. "You'll find no bombs here," he says.
In one large room, boys and young men are learning the Koran.
In other classrooms the lessons are Islamic law and history, science and English.
Musharraf has ordered all foreign madrassa students to go
During the 1980s thousands of madrassas were set up using money from the US and Saudi Arabia.
Fighters were indoctrinated and trained for the jihad in Afghanistan to repel the invading Soviet Union.
Mufti Mohammed Naeem denies his is one of them.
"We have never received even one rupee from the governments of Saudi Arabia or America. This institution runs on donations from local people."
And it costs a lot to run the madrassa.
Many of the students are from poor families. At the religious school they are educated and even get their meals for free. The foreign students pay just $50 a month.
Jamia Binoria will reluctantly comply with the government's order to expel foreign students.
But Mufti Naeem denies there is a link between religious schools and the bombings in London.
"Britain is saying that one boy went to some madrassa. How can a single trip make him a terrorist when all his education is done in Britain? Today you have also come here and now if you return to Britain you could be called a terrorist too."