Because they hear them every day.
Scots-born pupils at this Glasgow comprehensive – thanks to a decade of steady immigration – are now routinely exposed to the chat in an estimated 30 languages.
And, say teachers, it is starting to rub off on them.
So much so that the school is expanding its capacity to teach languages amid solid demand.
Gillian Campbell-Thow, the school's principal teacher of modern languages, said: "Given our catchment area across the north of Glasgow we have children from all sorts of different ethnic backgrounds.
"Just take Sighthill. There we have a real tapestry of languages. For many of our children, speaking or hearing different languages is now normal."
All Saints' catchment may be multi-cultural, but it isn't posh. More than a third of the roughly 1000 pupils at the secondary get free school meals.
Yet as schools across Scotland quietly drop modern languages, this August the Barmulloch-based comprehensive will add a fourth, Russian, to its curriculum. That is on top of French, Spanish and German already taught.
Few state comprehensives in Glasgow's suburbs offer that kind of choice.
Mrs Campbell-Thow passionately believes languages shouldn't just be for youngsters from leafier suburbs.
She said: "You can't deny someone part of the curriculum because of their postcode. But I am from the top of a scheme in Stevenston, so I would say that, wouldn't I?"
The teacher – who also acts as Glasgow's city-wide champion for her subject field – reckons all kids can gain from a bit of French, German or Spanish, whether they turn in to multi-lingual experts or not.
She said: "People think languages are something that can help you 'over there', if you get a job abroad or travel a lot.
"That's true. Of course, they look great on your CV. But they can come in handy right here in Scotland. What if you have a job in a cafe?
"You are going to get bigger tips if you speak to foreigners in their own language. You don't have to be completely fluent or speak perfectly to communicate."
Few argue over the education merits of a second or a third language.
Even fewer quibble with the life-changing job opportunities they bring: Scotland has a desperate language skills shortage.
But Mrs Campbell-Thow believes languages open the world for children – whatever their background.
She said: "The way I look at it is that every class has to be a Mini-France or a Mini-Spain.
"We are doing children a big dis-service if we don't teach them about another culture. Because you can't learn a language without learning about the culture of that country. And I think that does an awful lot to promote tolerance."
This principle means languages aren't just for language students.
At All Saints, languages highlighted in art, music and religious studies, where, for example, Mexico's Day of the Dead or Dia de los muertos is studied.
Children learn foreign cuisine with tasting sessions at French and Spanish restaurants, check out foreign films at the GFT and use Celtic's Learning Centre (the club after all has a multi-lingual playing and coaching staff) to boost language and literacy.
Outsiders are impressed. Last year senior pupils at All Saints came joint first in a national award for European Day of Language Celebrations.
They shared their prize with Madras College, St Andrews. Yes, a secondary in Barmulloch ranks alongside the school attended by professors at Scotland's poshest university.
Scotland's record on modern languages – never good – has been getting worse in recent years.
In 2001, then education minister Jack McConnell decided that the subject should no longer be compulsory up to 16.
As we revealed earlier this month, this now means that just 77% of Glasgow S4s stick with, say, French, compared with 91% a decade ago.
Glasgow's record has been mixed. Some schools, such as All Saints, remain enthusiastic about languages. Others not so.
One, Govan High, the city's smallest, has admitted its focus on vocational education has posed real problems for languages.
Govan has just one teacher. All Saints has six dual-language educators and, for the first time in years, has a new foreign language assistant arriving after the summer.
Foreign languages formally ceased to be a core subject for 2013-14 – sparking expectations even more children will drop the subjects.
Yet more than half of children at All Saints in S4 have decided to stick with languages.
Stephen Engles is one of them. He's doing both Spanish and German and is pretty clear about why.
He said: "You get paid more if you speak more languages."
But he has got interested in the countries too.
He added: "I love football from Spain and from Germany; I'd really like to go to Germany; I'd really like to work abroad."
Chantelle Weldon dropped French to take up beauty. Now she is back learning Spanish in an SQA Language for life and work qualification. Why?
She said: "The Spanish have such nice clothes. I really like Spain."
The number of students sitting highers are up too, to 14 for French and 10 for Spanish next year.
And these children are really reaping the advantages of going to a multi-lingual school.
Pupils who are native speakers of French, for example, are working alongside their Scottish-born classmates.
The jargon for this is Peer-Assisted Learning. Mrs Campbell-Thow likes the abbreviation for such teaching. "You learn best from your PAL," she says.
Next year All Saints will also present youngsters for Advanced Higher Spanish and languages baccalaureates.
FEARS over a lack of foreign language teaching in Glasgow has been raised at the Scottish Parliament. But it is a different story at one city comprehensive, as DAVID LEASK reports