It became the revolution's headquarters, with classrooms turned into ministries as the revolutionaries organised a government.

Shah loyalists were executed on Refah's roof. Today it serves as a school for girls.

'Oh, holy warrior, oh symbol of honour,' the schoolgirls in their modest little headscarves sing in unison, 'You are the protector of our nation and faith. Your words lead us to health. Khomeini, oh, Imam! Khomeini, oh, Imam!'

Though the slogans remain the same, the Iran for which the Refah School is preparing its 700 students is far different to that of 25 years ago. Though politically still a theocratic dictatorship, Iran is no longer the country where people once swore they saw Khomeini's face in the moon, a sign from God that he was to be their temporal leader.

Its people are younger, smarter, more cynical and more modern.

'The revolution put us at least two decades ahead of Arab and Muslim countries,' said Hamidreza Jalaipour, a University of Tehran social scientist. People in those countries now want religious government. We've already experienced that.'

A quarter of a century on, the revolution that started at Refah School casts a long shadow on the wider world.

'It catalysed Islamic movements across the world,' said Rasool Nafisi, an Iranian-American professor of humanities at Strayer University in Baltimore. 'New militant assertions of power by Muslim clergy are being heard across the Muslim world.'

Certainly the Islamic revolution radically transformed Iran. A 444-day hostage crisis at the American embassy destroyed ties between Tehran and Washington.

The eight year Iran-Iraq war left hundreds of thousands dead and wounded.

Up to 25,000 were executed during Iran's long, night of terror in the early years of the revolution, says Amnesty International.

The clerics' shock troops enforced Islamic rules against alcohol, dancing and pop music, bans that continue today. They took over the courts, intelligence services and the military. They also presided over the stifling of dissident voices and the creation of a police state that continues to force women to cover their heads. Militants despatched overseas became instruments of terror.

But today's Iran must adjust to new domestic and international realities. US troops occupy Iraq to the west and guard Afghanistan to the east. Europeans demand concessions on terrorism and weapons proliferation in exchange for badly needed foreign investment.

Iran's clerical leaders are under pressure to introduce reform. Over the past few years, a group of people within the regime have tried to change Iran, led by President Mohammad Khatami, the smiling cleric who was elected with huge majorities in 1997 and 2001.

Many reformists were recently barred from running again by the hardline judiciary, setting off a political crisis that has yet to abate.

But increasingly, politicians are not the driving force for change in Iran. Two thirds of Iranians are under 30, a generation of well-educated discontents.

'We were looking for freedom and social justice,' says Fazel Maibadi, a liberal cleric in the spiritual centre of Qom. 'We're still a long way from that.'