German primary pupils' much better ranking than its secondary pupils in international literacy tests has led to renewed calls for a comprehensive secondary system.
The Progress in International Reading Literacy Study, published last week, ranked German 10-year-olds 11th out of 35 countries. Yet the reading skills of Germany's 15-year-olds ranked 21st out of 31 countries, according to last year's Programme for International Student Assessment survey.
In Germany, 11-year-olds go from mixed-ability primaries to one of three tiers of schooling, depending on ability. But in the wake of the international survey, GEW, the main teachers' union, has stepped up demands for a "one-school-for-all" system with mixed-ability secondary classes.
PIRLS had confirmed that Germany's primary schools were internationally competitive, said the union, which also advocates a longer primary school phase.
However, the Kultusministerkonferenz, which represents the education ministers of the 16 German states, rejects this, but concedes that primaries have been more successful than secondary schools in finding the right teaching approach, as well as in developing children's abilities.
Teachers see mixed-ability classes as "a challenge, not a handicap," said Marianne Demmer, a GEW spokeswoman on school policy.
"They select a variety of learning activities to suit different children within the one class," she said.
However, she said that instead of motivating and encouraging pupils as primaries do, German secondaries "select and reject".
"They demote children to lower-ranking schools if their performance is not up to scratch," she added.
Recent nationwide polls showed parents also hold primary schools in high esteem. Close contact with teachers, extra tuition opportunities and community service back-up in many schools foster an atmosphere of mutual trust.
And, according to the PIRLS survey, children at primary schools are relatively well integrated whereas PISA revealed that the gap between rich and poor students' results is bigger in Germany than elsewhere.