The best-scoring students in Switzerland are from canton Schaffhausen, according to a breakdown of results from an international survey.
The canton in eastern Switzerland came out on top in all three categories – science, mathematics and reading. St Gallen students also scored well across the board.
Zurich students were the worst in German-speaking Switzerland, according to the Organisation for Economic Co-operation and Development's Programme of International Student Assessment (Pisa).
Overall, Swiss students were strongest in maths and weakest in reading. Fribourg and Valais were the two best-performing French-speaking cantons while Italian-speaking Ticino made significant progress compared with 2000.
The Pisa test evaluated the performance of 15 year olds at the end of their obligatory schooling period. The test in 2006 was the third time Switzerland's students were evaluated as part of the programme.
The study also set so-called competitive levels, benchmarks at which students are deemed to be at risk of facing problems in their transition to the working world.
The Pisa survey found that 18 per cent of Zurich students did not reach the first level, the highest in the country.