A secondary headteacher in Berlin is warning German-speaking parents not to send their children to his school after the number of pupils with German as their mother tongue dropped to just five out of a total of 339.
Bernd Boettig, head of Eberhard-Klein secondary school, said: "If German parents turn up here, I feel obliged to advise them to register their children at another school."
He said it was his "pedagogic duty" to do so because the language difficulties of other students would slow down classes and limit the learning opportunities for native German speakers.
His call has highlighted the impact of a change of rule in Berlin schools in the mid-1990s. Until that point, they were forced to fulfil integration quotas which required at least 50 per cent of students to be native Germans. At the time it was thought that second-generation immigrants would not have the same language problems as their parents.
Just 1.5 per cent of pupils at the Eberhard-Klein school speak German as their first language, and the situation is similar in other Berlin districts. At the nearby Gerhart Hauptmann secondary modern, for example, 90.4 per cent of students are immigrants.
Eighty per cent of the school's students are of Turkish origin and a further 15 per cent are Arabs. The rest are made up of Albanians, Vietnamese, Africans and students from the former Yugoslav republics - and the five Germans.
Schools minister Klaus Boeger confirmed that many German parents have decided to move their children to other schools in the capital.
He said: "Many parents feel that by sending their children to a school with a high percentage of non-native German students, their educational progress will be affected."
A teacher at the Eberhard-Klein school said that this has already proven to be the case, and added that even the best students barely scrape a pass on assignments and tests.
The high proportion of immigrant children in Germany's schools has been blamed for a disappointing result in recent international comparative studies. It has also led to calls for language tests to be introduced before the first year of primary school. Under the proposals, children who lack the necessary skills for school will be offered pre-school German courses to get them up to a basic standard.
Mr Boeger, who supports the plan, said that he would also like to cut class sizes at schools with a high proportion of immigrant students.