The Organisation for Economic Co-operation and Development's 2001 PISA (Programme for International Student Assessment) study, released at the end of June, ranks the 16 German states by reading, mathematical and scientific literacy scores for 15-year-olds.
Prosperous states Bavaria and Baden-Wurttemberg came top. But only Bavaria scored higher than the OECD average. The poorest states and those with large immigrant populations like Bremen performed worst, only just above Mexico and Brazil, the poorest performers in the international study.
The analysis, carried out by Berlin's Max Planck Institute, showed wide disparity in performance both within and between states and confirmed the OECD's conclusions that German literacy levels depend more on social background than in virtually every other developed country.
"The differences between best and worst are bigger than in other OECD countries including Britain and the US," said the institute's Juergen Baumert.
The huge variation has caused a furore, with politicians criticising state governments for running education departments as their own fiefdoms.
Chancellor Gerhard Schroeder said that what had in the past been praised as "federal competition" had turned out to be "state egoism at the expense of students".
A parents' lobby group, the Federal Parents Council, is preparing to challenge the system in the constitutional court. An education system run by individual states does not guarantee the right enshrined in the constitution to equal access and opportunity throughout the country, they said.
"The chances of German children should not be dependent on where they live," echoed Federal education minister Edelgard Bulmahn.
However, the states are already bickering over the implementation of national standards and tests agreed by education ministers in May. The government wants testing in core subjects to be in place by 2004.