When students return from the Shackleton Exchange, they are two inches taller," explains Nick Mair, director of languages at Dulwich College, a selective private boys' school in South London. The trip is named after college old boy and legendary polar explorer Ernest Shackleton.
Perhaps unsurprisingly, however, the boys do not sail to the Antarctic to get stuck in the pack ice in pursuit of personal development. Instead, they are sent away to spend three weeks in a French school.
Staying with local families, these students are forced to get to grips with the language, culture and schoolwork, without the comfort blanket of their own teachers or friends.
It is a scary proposition for 14-year-olds (and their parents) in these risk-averse times, but a valuable one, Mair insists.
"It is essentially an old-style exchange," he says. "What is new is making it work in a world where everybody is terrified of health and safety."
Indeed, there seems to be relatively little dispute about the benefits of old-fashioned foreign-language exchanges among teachers and other experts. "I've observed that one full day of an exchange is equal to about a week's teaching, and each trip is worth about half a grade at GCSE," Mair says. "That is very good value if you think about it."
School exchange trips, at least until recently, have been seen as a rite of passage for many British children, to be enjoyed and endured in equal measure. Indeed, swapping stories about the nightmarish Parisian family you stayed with or the furtive snog you had with the gorgeous older brother of your exchange are staples of dinner table chat.
And then there are the opportunities to grow academically. Swapping swear words in a foreign language can be an important bonding experience and certainly increases the vocabulary - there is nothing quite like the outrageous laughter of two teenage girls from France and England sharing 20 different words for "penis". Whatever happens, you learn something about foreign culture.
And yet all indications suggest that exchanges - along with wider language learning - are in decline.
Child protection fears
A report from the UK's National Foundation for Educational Research in February showed that students from England reached the lowest level of competency in foreign languages out of 14 European countries (alongside the French). So it is not as if the English couldn't do with some linguistic immersion therapy. Even so, principals' leaders in the state sector report a significant decline in "home stay" language exchanges in recent years.
While figures show that the number of people learning English around the world is rising fast, British schools are increasingly less keen to place students into foreigners' homes and then return the favour. The numbers studying modern languages have also declined, meaning that there are fewer potential exchange students to satisfy the demand from abroad.
Fears over child protection have been cited as a key reason: at least four councils in Wales have banned home-stay exchanges. Students must instead stay in groups in hostels and hotels and visit their exchange families in pairs.
"Already, these kind of school exchanges were starting to diminish in the late 1990s," says modern foreign languages specialist Dr Shirley Lawes from the University of London's Institute of Education.
She cites the rape and murder of British schoolgirl Caroline Dickinson on a school trip to Brittany in 1996 as the tipping point in a cultural shift towards risk aversion.
"Paradoxically, her murder took place in a youth hostel, not in a family home," Lawes says. "But from around that time, parents, in an unwarranted way, started getting concerned about their children going into a strange family."
The introduction of the Safeguarding Vulnerable Groups Act 2006 and the launch of the Independent Safeguarding Authority in 2009 (now part of the Disclosure and Barring Service) also ushered in an era of confusion.
New rules insisting that host families would have to undergo strict criminal records checks were met with outcry, as critics feared families would be put off hosting.
This prompted Sir Roger Singleton, then government adviser on child safety, to confirm that there was no known incident of a child being abused while staying in a host family on a school exchange. A full review followed and schools were told that there was actually no requirement to carry out checks on host families in either country.
Schools, of course, still have the heavy burden of assessing the possible risks to their charges while they are away, but this is the same as with any school trip.
"While the vetting and barring regime has been overhauled over the past few years, little has changed with regard to host families," confirms Dai Durbridge, education lawyer and partner at Browne Jacobson law firm.
'Trust and common sense'
Despite these threats in recent years, many schools do still successfully organise foreign-language trips.
"It's all about trust and common sense," says Hilary French, president of the Girls' Schools Association and headmistress of Central Newcastle High School. "If you're going to have successful exchanges, you are going to have a very close relationship with the school you are exchanging with.
"We trust the girls' school in Stuttgart we go to, and they trust us. I have been on our school's German exchange and the girls always have a contact number of the teacher in charge - they have their mobiles. Part of the experience is being immersed in the family - you don't want to see that diluted."
Indeed, in the era of 24-hour mobile communications, you might argue that it is safer than ever for a teenager to stay with a relatively unknown family. Students can even make email and Skype contact with their host families before departing, which offers further reassurance to parents.
But Brian Lightman, general secretary of the Association of School and College Leaders, says that schools' reluctance may not just be attributable to nervousness over child protection.
"There's been a cultural change, certainly, in this country and families are less willing to take someone into their family," he explains. "They would much prefer for the children to go on a trip, without the hassle of looking after someone at the weekend. People are so fearful now about an unknown quantity."
Lightman, a languages teacher with many years' experience of exchanges, adds: "Teachers have also got enormous pressure on their time and running an exchange is a big job.
"With the threat of Ofsted arriving, you can understand why, sadly, some people will come to the conclusion that it is easier to take a straight trip."
And while straightforward school trips - with a linguistic element - are no doubt enriching, many teachers believe that language-learning opportunities are relatively thin.
"It's a real shame," French says. "We are not renowned for our ability to speak other languages and get on with other cultures, so the move away from traditional exchanges is a retrograde step. "If a school takes a trip to a French chateau to do some activities, it is a step removed. You're always with English people, your friends, you're not really living in the culture. There's lots of security and comfort blankets.
"You might speak English with your friends on the way to the baker's and only say a couple of sentences of French while you're in there."
Education authorities in France have also voiced concerns that young French people are speaking very little English when on educational trips to the UK.
So is there a risk in England, at least, that exchanges will become the preserve of private schools and selective state grammars? Are children whose parents are not able to arrange their own "home stays" through friends or private firms doomed to linguistic failure? And what about the schools whose catchment area may not have the kind of reputation wanted by a potential partner school? The kind of area where parents might not be keen to play host to foreign teenagers?
But some believe that any obstacle can be overcome if a school really wants to run an exchange programme.
At the Ashcombe School, a non-selective state school in Dorking, Surrey, staff believe that exchanges are within the reach of schools, as long as the senior management is on board. Ashcombe organises French, German and Spanish exchanges every year.
"One of the most important things is creating the time to organise the exchange - you can't expect normal teachers with full timetables to do it," assistant headteacher Helen Myers says. "When we launched as a language college in 1998, we employed a special member of staff to set up the exchanges, and over the years they have become an established part of school life.
"The funding is now gone for that, but we still pay for the same person to come in part-time to keep things running. Parents trust the trips now because so many people have gone on them and they trust the person who has been organising them."
Myers says that investing in running the exchanges has also created a "virtuous circle", which encourages language teachers to come and work at the school.
"They usually come on the trips at first, but as time goes by they may be able to take charge of the trip," she says.
But the main thing, she explains, is support from the school's leadership team: "They have to be on board. You can't just say to the teachers, 'Get on with it.'"
Crickhowell High School in Powys, Wales, also runs language exchanges, but sees them as only part of a much wider international cross-curricular approach.
A group of students is travelling to Quebec next year after hosting teenagers from the Canadian province last year. Students will stay with families, get to grips with the quirky Quebecois French and learn about their fascinating culture.
But trips are not always linguistically motivated: the school is also involved in exchanges with a school in Singapore, where students will be exploring student leadership, and with a school in Virginia, US, where the programme of activities includes looking at global conflicts, immigration and ethnicity.
"You can have a situation where kids who go to France for a few days follow their exchanges around school for a week and get nothing out of it," deputy headteacher Rob Ford says. "This is what we avoid doing. We want to eke as much out of our trips and visitors as possible."
For those schools that are struggling to get a full-scale exchange going, there is still hope.
The British Council, which promotes British culture abroad, believes that the scope for linguistic and cultural interaction in all types of school is more substantial than ever. There is now a plethora of schemes encouraging international partnerships between schools, some of which put young people in contact with each other at the touch of a button.
Some 3,541 schools in Britain are involved in the Comenius programme, a Europe-wide scheme that funds schools to set up partnerships and exchanges and offer in-service training for teachers in a school abroad. It also helps schools to arrange for foreign-language "assistants" or native speakers intending to be teachers to give small-group conversation lessons.
And about 5,200 schools across the world have benefited from Connecting Classrooms, which helps schools to set up partnerships and joint projects with schools abroad.
Approximately 420 schools in the UK are also involved in eTwinning, helping them to become part of a huge online community of schools around Europe. The British Council says that this project helps to motivate children by putting them in direct contact with their peers, and encourages communication in a foreign language.
"Traditional exchanges still happen in France and Germany, but in England children don't do it as much," Vicky Gough, schools adviser at the British Council, says. "A lot of people don't feel confident to stay in people's homes any more. There's been a big decline in teaching languages in Britain, but there's still a strong willingness to have a cultural exchange.
"Nowadays, students are more likely to find a foreign teacher in front of their class, receive a letter from a foreign child or hold a Skype conversation. Writing a letter to a real child in another country and finding out about their town is much more motivating than writing to an imaginary person."
So, while the old-fashioned exchange is becoming, well, less fashionable, this may not mean that schools are growing more insular and cut off from their neighbours. Anything but. Even though Britain has a long way to go on languages, schools seem to be finding ways to offer their charges a particularly international outlook.
And for those who enjoy nothing more than chatting about the first time they tried some saucisson, that - at the least - has to be a good thing.
'UHT was warm and tasted weird'
I was 13 years old when I was sent to Redon in Brittany, France, a small town twinned with my home town of Andover in Hampshire.
My strongest memories of this trip are all connected to food.
First, there was the milk - everyone in Britain still had a pint or two delivered every day, but here it was UHT and was kept in cartons in a cupboard. It was warm and tasted weird.
Then came the final special teatime. The family had a joint of beef. They put it on the open fire. I was sitting there thinking, "In England we cook meat in ovens."
After about 15-30 minutes, they picked up the still dripping bloody hunk of meat and served it up. A piece was placed on my plate. Blood ran on to my chips. I knew that the point of cooking was to heat food and kill bacteria. I had never heard of rare beef.
My visit made me realise how entirely futile it would be to learn French as I was already miles behind a five-year-old at age 13. And I never wanted to visit France again.
Helen Ward, TES journalist
"It's not necessary"
Johann was a sulky fellow who resisted participation at every turn. Hence his response to all suggestions: "It's not necessary." Activities of all kinds, from visits to the Tower of London to ice skating, were batted away with this most utilitarian of swipes.
When I returned to Johann's natural habitat later that year, I discovered that he genuinely didn't find it necessary to leave the house very often at all. He just stayed in playing on his computer.
But his mother took to me, and bristled my pride by asking me to write a recipe for tea. Such a recipe had previously been lacking in her life and particularly in her tea-making, which was poor.
I left their home with the mother very happy that she now knew not to remove tea bags from a tea pot only seconds after the water had grazed their surface, and the teenager happier still that he could play his computer games in peace.
Alex Smith, political researcher
Beware the sausage
As a shy but enthusiastic student of French and German, I was both thrilled and horrified by the prospect of engaging in foreign language exchanges.
My French exchange friend was Edwige - the liveliest person you could meet. She was of such a sunny disposition that she made me feel gloomy. But I was going through a somewhat Gothic phase.
Memories of my trip to her house in France include eating a sausage made by her father from a pig he had slaughtered himself. I recall him chuckling, eyes twinkling mischievously, as I ate a slice and then chopping off more, which I politely ate as well.
It wasn't until about the eighth slice of this rustic saucisson that I realised he was not going to stop slicing before I stopped eating. Concerned by the large blobs of fat and distinctly piggy odour, I halted eating with a loud chuckle and a facial expression of intense gratitude. I've exercised caution around French sausages ever since.
Irena Barker, TES journalist.