Some protesters hurled cafe chairs in Rome's Piazza Navona
School pupils, university students and teachers have staged demonstrations across Italy against a school reform law just passed by parliament.
In Rome's Piazza Navona, a popular tourist spot, several people were lightly injured in a clash between left- and right-wing students.
The reform package is expected to cut the education budget.
In primary schools there will be just one all-purpose teacher per class and a grade system for pupils' behaviour.
The package will reinstate a 10-point system for grading pupils' conduct, aimed at curbing bullying.
The government decree became law on Wednesday with 162 senators voting in favour and 134 against.
The leader of the centre-left opposition Democratic Party (PD), Walter Veltroni, vowed to push for a national referendum to get the decree repealed.
Wednesday's demonstrations followed similar protests against the reform package in the past two weeks.
In Milan and Naples students occupied train station platforms, the Italian news agency Ansa reported. Several other cities also saw protests on Wednesday, including Brescia, Cagliari and Padua.
Some teachers staged open-air classes for students.
The right-wing prime minister, Silvio Berlusconi, said: "It's a pity to see so many young people fooled and misled by the left."
Education Minister Mariastella Gelmini said "we will bring seriousness and merit back to schools".
Students and teachers plan to go on strike on Thursday.