Philip Hensher: Can you say good morning in Bengali?

Even if we learn Mandarin to negotiate over bulk prices for widgets rather than read the poetry of Li Po, the humanising influence will make itself known

A few months ago, I was teaching a creative writing class to nearly 20 undergraduates – bright, well-informed and intelligent students at the excellent university where I lecture.

There is a fictional mode which is now rather out of fashion, but which writers need to understand: the authorial intervention. Looking for a famous example, a celebrated line of Flaubert came to mind, and I wrote it on the white board. It is the savage moment in Madame Bovary which so shocked Flaubert's first readers, and without thinking, I wrote it as it came to my mind: "Emma retrouvait dans l'adultère toutes les platitudes du mariage."

There was a puzzled, uniform, eager look in the class. I realised that not everybody would have done even GCSE French, and I asked for someone to help out. As it turned out, not one of my highly polished and able students was up to even guessing at the meaning of a very simple line in French. I hid my dismay, explained and quickly translated. We went on.

Things have changed. I think, when I went to university to study English language and literature, the majority of my peer group had studied a foreign language to A-level. As it happens, Madame Bovary was one of my set texts at A-level, which is probably why the quotation came to me most readily in French. I am by no means a specialist, but the residue of what seemed a necessary part of a literary education has remained with me. It might only mean passing the time of day with neighbours in Geneva, or someone standing in a bus queue in Berlin or Rome; recently a recommendation sent me to the untranslated novels of Patrick Modiano. If I were 20 years younger, my education would probably have fitted me to shrug, and smile apologetically, and I would know nothing much of Modiano's elegant novels.

The Government has now decided that foreign languages are, after all, a vital part of every schoolchild's education. The new "English baccalaureate" qualification, rewarding students who pass a range of subjects at GCSE, will include one foreign language as a compulsory element among five. It is easy to see how obtaining the baccalaureate will become a minimum requirement for admission to a good university. It may address what has become a catastrophic situation.

The total slump in the numbers of students studying foreign languages at A-level is an astonishing phenomenon in our increasingly global existence. It has largely happened since the Labour government's decision to allow students to drop them after 14 from 2004. Nobody, surely, could have predicted that the new ease of movement between EU member states would have been accompanied by an evident complete lack of interest in speaking to the people one might meet.

But that is what has happened. This year, a mere 13,850 students took French A-level; a desultory 5,548 took German. That is a drop of about a third in 10 years. There is plenty of evidence, too, to suggest that foreign language A-levels have tried to maintain some appeal to students by lowering their demands. A Higher Education Funding Council-funded report in 2009 observed that foreign-language departments at some universities were obliged to provide remedial lessons for people who had taken A-levels in the language, because they had inadequate understanding of grammar and inextensive vocabulary. I may be completely wrong, but it seems unlikely to me that any A-level in French is now asking students to read a long and complex novel like Madame Bovary in its original language.

When Sherlock Holmes, on the train, remarked to Watson on the new board schools rising above London, he called them: "Light-houses, my boy! Beacons of the future! Capsules with hundreds of bright little seeds in each, out of which will spring the wise, better England of the future."

That idealistic vision of the humanising purposes of education has more or less disappeared from public policy. We don't recommend the teaching of foreign languages simply because it makes us more human; because great books are not always written in the language we happen to speak; because it is important to understand how people different to us speak and feel.

If it is justified at all these days, it is in terms of opportunities to make money, rather than Flaubert or wisdom. The decline in the teaching of traditional, European languages has been abetted by a false belief that "everyone" in Europe speaks English; there is no need to learn anything but the international language of business, English. The only justification for the appearance in curricula of Mandarin and, to a lesser extent, Arabic, is that we are going to need to do business in those parts of the world – these are languages which are showing rises against the general trend of language learning. The relative solidity, too, of Spanish compared to other European languages probably reflects a sense of the business importance of South America in the future.

The broadening of what is meant by foreign languages in schools is surely to be welcomed, however, whatever the reasons behind it. Even if we learn Mandarin in order to negotiate over bulk prices for widgets rather than read the poetry of Li Po, the humanising influence of living in very different patterns of thought will make itself known. It seems astonishing that many of us live in very multilingual circumstances without feeling much curiosity about the languages we hear every day – walking down my nearest high street, I would expect to hear a dozen languages, African, Slavic, Indian and far Eastern. To be able to say good morning to our Bengali, Polish or Cantonese-speaking neighbours would be a wonderful thing.

So much of what we learn at school proves, in adult life, not worth the recall. They are exercises which we go through to stretch the mind's capacities. Afterwards, we rarely find that we need to remember the structure of the atom, harmonise a Bach chorale, remember what synecdoche is or recall the order of the Factory Acts unless those things turn out to be our professional speciality. But foreign languages, once learnt, stick like burrs to wool. They are not just means of training the mind in complex intellectual structures, but of communicating with people, lifelong, in ways we can't predict. They make us fuller, more imaginative people, too. The Government is absolutely right to make them a pillar of the proposed English baccalaureate.