The Latvian 17-year-old was penalised by Edexcel, Britain's second largest exam board, after failing to follow the rubric of his exam last summer.
But the mark scheme states that students should be rewarded for the quality of their language and conversation skills.
His school - an independent institution in the south-east of England that does not want to be identified - contacted The TES after we disclosed that the Qualifications and Curriculum Authority is conducting an investigation into exam grading irregularities at GCSE and A-level. Eton College, for example, reported that two of its pupils, who scored zero for a Russian AS paper, later achieved As after a re-mark.
Under the rules for his Russian oral exam, the Latvian candidate was supposed to speak about food, diet and health in Russia. Instead he spoke about his own food and drink preferences.
The mark scheme for the AS oral states that students will be assessed on three criteria: knowledge and understanding; response to questions; and quality of language.
Edexcel's examiner decided that the student could not be awarded any marks for knowledge and understanding, since he had not spoken about Russia. He then judged that marks could not be awarded for the other two criteria either, since a "rubric offence" had been committed.
The school contested the ruling, but the board's decision was upheld by an appeals board. The teenager will re-sit the module this year.