The regions argue that the ley de calidad, with its exhaustive curriculum requirements, infringes their right to self-government. Currently central government dictates up to 55 per cent of the curriculum, a proportion the regions, known as autonomous communities, fear will grow.
Teachers and students staged huge demonstrations against the legislation when it was passed into law late last year by Jose Maria Aznar's conservative government, which enjoys an absolute majority in parliament.
Opposition education spokesperson Carme Chacon said: "This is a consequence of the style of the Aznar regime, which is against the educational community and against the autonomous communities." Due to be implemented from September, the Act requires pupils to choose between academic, vocational training or "integration into employment" paths by the age of 14, two years earlier than elsewhere in the European Union. It gives academic status to religious education; introduces a more rigorous system of teacher training and assessment; and provides public funding for certain private schools.
The legislation will also reintroduce an exam at the end of secondary school for academic pathway pupils to obtain the bachillerato certificate required to enter university.
The test, which will include an oral examination of the students' chosen foreign language, will be used alongside their average score to assess their final grade. Students who want to go to university will then have to take a separate entrance exam.
The autonomous communities must appeal against the legislation by April 13.