At break-time at Herbert Hoover Secondary School, Taner, Mohammed and Tugba frequently discuss the results of the Süper League, Turkey's top-flight football competition.

Not so strange for three youngsters of Turkish origin perhaps. But what is unusual is that the students, whose mother tongue is Turkish, are discussing the topic in German.

"If the teachers hear that we are speaking Turkish, then they say to us: speak German," explains one of the boys.

"It's good for our future. In every job, we have to talk in German," says another.

Herbert Hoover Secondary School in Berlin unleashed a storm of debate when it made speaking German on school grounds and on educational excursions compulsory.

Harsh criticism

School principal Jutta Steinkamp was accused of discriminating against immigrant children by members of the Left party.

But last year the German National Foundation awarded Hoover school with a 75,000 euro ($100,000) prize, saying the school helped immigrant pupils to improve their language skills.

And Steinkamp said an external commission of experts has just said the introduction of the measure has improved discipline and academic standards. And the idea is being taken up by other schools at both home and abroad.

"We had a lot of aggression. And pupils I talked to, they said: well, there are quite a lot of misunderstandings and there are the different languages, we don't understand them, perhaps it was an aggressive word, I don't know and so our pupils started to fight with each other," said Steinkamp.

Widely accepted

The teachers do not have to enforce the ban with sanctions, she adds, because most pupils have accepted the rule by now. At home, nine out of 10 of her students don't speak German. Turkish, Polish or Russian are more common.

"School is the only occasion where they speak German. I mean it's natural that in their communities, in their families they speak in their mother tongue. So they have to practice it here. Where else? Where else could they do it?"

Steinkamp says the commission confirmed the positive effects on her pupils' average grades. That's why other schools in Germany have already started copying the model. Swedish and British schools have also expressed an interest.

But, 10th-grader Tugba says, the regulation doesn't always suit her. When she talks about boys with her Turkish friends, she simply has to switch back to her mother tongue. Some things are just easier to explain in Turkish.