The largest non-Muslim minority in Iran, the Bahais, are persecuted in many ways - one being that they are forbidden from attending university. Some study in secret, but for those who want to do a postgraduate degree the only solution is to leave their country and study abroad.
"I remember my father showing me the scars he had on his head from when he used to be beaten up by the children of his town on his way to school," says Shirin. "So, of course, I didn't tell my father that I was experiencing the same when I was growing up in Iran in the 1980s. I knew he prayed and hoped that the world would get better."
In fact, persecution of the Bahais only increased following the Islamic Revolution in 1979.
And when Shirin's son, Khosru, started going to school, she had to hide more bad news from her father.
"I did not tell him that the children of the children of the children who left him scarred, are now calling my son untouchable," she says.
When, in the eighth grade, Khosru told the other children he was Bahai they dropped him like a stone.
"The kids wouldn't touch me," he says, "and if I were to touch them, they'd go and take a shower."
Since the creation of the Bahai faith in the mid-19th Century, the Iranian Shia establishment has called them "a deviant sect", principally because they reject the Muslim belief that Mohammed was the last prophet.
On official websites they are described as apostates, and as "unclean".
But it is when a student has finished school that the problems really begin.
As a Bahai, Shirin was told she could not enter university. Her only option was to secretly attend the Bahais' own clandestine university - the Bahai Institute for Higher Education (BIHE), set up in the mid-1980s by Bahai teachers and students who had been thrown out of Iranian universities after the revolution.
Shirin enrolled in 1994. At that time, only two BA courses were available -in Science or Religious Studies - so she decided to study comparative religion.
Lectures took place in improvised classrooms in private homes all around Tehran. It took six years to complete her course, and it was then that she hit an impenetrable wall. There was no scope to do an MA or a PhD, and there was no scope for employment where her skills could be used.
Soon afterwards, a wave of crackdowns on the Bahai intelligentsia began, with raids on clandestine classrooms and the arrest of many BIHE teachers. Shirin saw her world was closing in on her. So when she heard about a domestic worker's visa scheme in the UK, she jumped at it.
"I applied straight away without wasting time, it didn't matter what the visa was called. I had to leave," she says.
Shirin arrived in the UK in 2003 and combined her domestic work with an evening job at an Italian restaurant in Scarborough. But she never forgot what she came to do, what she must achieve.
On a dark and smoggy English morning, she boldly walked through the doors of Birmingham University, and announced that she had a degree in religion from an underground university in Tehran.
To her great surprise, a week later, she was summoned back and was offered a place.
Find out more
Listen to Lipika Pelham's report on the Bahai, The World's Faith, for Heart and Soul on the BBC World Service
"It was more than a miracle - it was beyond expectation, beyond my wildest dream," she says. "Till today, I feel it was the best reward I received for never compromising my faith."
Shirin finished her degree in 2006 and left the UK to join her brother in the US, where many of her family, friends and co-religionists have, over the years, found sanctuary from persecution.
But soon another crackdown against the Bahais began, at home in Iran.
In 2008, seven members of the Bahai administrative body, Yaran, were arrested and charged with among other things, spying for Israel. After a trial in a Revolutionary Court in 2010, they were sentenced to up to 20 years in prison.
At this time another young Bahai woman, Mona, was applying to university in Tehran.
"I took an entrance exam at the University of Tehran - they were supposed to send a card saying how and where you should register if you were accepted, and you must write your religion on the card," she says.
"I wrote that I was not Muslim. There was an option that said 'other', and I ticked that box. There was no option for Bahai.
"When they sent back the card, they said, 'OK, you may register,' and in the place of religion, they wrote, Islam."
"In my belief, you're not supposed to lie about your faith even when facing death. So I wrote back, I was not Muslim. They said, 'Good luck, you can't enter university.'"
Like Shirin, Mona had only one option - the clandestine university, and it was an unforgettable experience.
"I remember the faces of all my friends who were coming from other cities in Iran, from far away," she says. "It took them maybe 16 - 20 hours to get to Tehran. Their faces looked so tired.
"It was really hard. We had one class from 08:00 to 12:00 in the east of Tehran, and the second class from 14:00 to 18:00 on the west side - it was exhausting! Sometimes we didn't have physical teachers, we had them over Skype, who were teaching us from the US, Canada."
After she graduated, she faced the same difficulties Shirin had experienced a decade earlier - and opted for a similar solution.
In 2009, she escaped to New York, via Austria, under an international religious refugee repatriation programme.
When I met her recently in Joe's Coffee, a lively meeting place for students and teachers at Columbia University, she had just completed her MA in Psychology. She was over the moon.
"It feels amazing, I can't believe it's all done and I'll even have a graduation! When I graduated from the BIHE, they arrested all my teachers, Bahai teachers. And we never had a graduation day."
The US is home to one of the largest Bahai populations in the world, their presence dating back at least to 1912, when Abdul Baha, the son of the faith's founder, Baha'u'llah, spent 11 months in the country, promoting the religion.
The BIHE degrees are accepted by most US universities - as Mona's was at Columbia University - and many BIHE volunteers are based in the US.
"Students and instructors in Iran can end up in jail just for being students and instructors. So they are not only doing something that is hard for them to do, but dangerous to do," says Prof Thane Terril, a convert to the Bahai faith who now runs online teacher training courses for post-graduate students.
"The motivation for the students is like a person in the desert without water."
Sipping coffee in the café of the former hotel, Ansonia, on the Upper West Side of Manhattan, where Abdul Baha once stayed, Shirin says that she could never understand what the regime has against the Bahais.
"Abdul Baha emphasised that the East and West must meet," she says. "I think the collective approach to life is what we think of as being the oriental or Eastern culture, and the individualist approach to life is considered to be Western. And when the two merge, you have a very beautiful culture."