He goes on to an equally perfect discussion of his chosen topic. Overall grade - A. And so it should be, for this candidate is a native German. But what is the point of a native English speaker assessing the accuracy and fluency of a native German speaker? Why are we both going through this?

These questions apply just as much to other parts of the exam. It is true that marks are given for ideas and task completion, but this is infinitely easier when the language is no problem. Working with synonyms or marking statements true or false may be rigorous tests in a foreign language, but not in your own.

Each year native speakers are entered for A-level and GCSE exams alongside English speakers for whom they were intended. All pupils are marked on the same criteria. But the skills tested are different. The native speakers invariably get the top grade, leaving the hardworking English speaker - having achieved far more in terms of skills - with a lower grade.

This is unfair, particularly as the high grades of native speakers will push even the better home-grown candidates down the scale.

Statistics on the subject are unavailable. The Department for Education and Employment has “just not thought about collecting” them. The Independent Schools Information Service could provide no breakdown of language exams. The Southern Examining Board has no figures, and the Qualifications and Curriculum Authority “doesn’t ask for that information”.

Nobody knows what percentages of exam grades are gained by native speakers - it is not seen as a problem. But this is a growing trend, particularly in German. In my school three English speakers and three native German speakers took the A-level exam this year - the Germans all got A grades. Another independent school entered two English speakers and 15 native German speakers last year - all the Germans got As.

There is an increasing readiness in Germany to send 16-year-olds to Britain for a year or two. Agencies in Germany make the possibilities a reality - for a price. For it is the independent sector that can accept these pupils. The schools boost their performance in exams and, possibly, their position in the league tables.

Although some German states require pupils on a year abroad to take German A-level, many German pupils have no real reason for taking the exam. “German is one of my three A-levels, but it won’t do me any good when I go back to Germany,” says Katharina Schilling, one of this year’s candidates.

Two solutions spring to mind. First, the native speaker could sit the same exam as other candidates, but with the marks being removed from the pool and awarded as a separate examination. In the longer term, candidates could sit a separate native-speakers’ exam, which would test more relevant skills. This kind of exam might also have more value in the foreign country.

But who should sit which kind of exam? It might be unreasonable to exclude a British child who speaks, say, Urdu at home from gaining a qualification in it. And a pupil who has learned Italian by going to school in Italy might want to take the exam. Then again, such children might best develop their language skills by doing something more relevant and demanding.

These decisions would have to be left to schools. But in clear cases where foreign nationals are here for a short time, a new kind of language exam would be fairer all round.

Garry Britton was until recently head of German at Pangbourne College in Berkshire