Schools were shut around France on Thursday as teachers, postal workers and other government workers staged a one-day strike. Tens of thousands of protesters marched through Paris and other cities.

As the marches were winding down, Mr Sarkozy went on national television and announced that he had asked the government to propose a law requiring schools to shelter students even on strike days.

'I have asked the government to introduce before this summer a Bill that will ensure that children can still go to school and that parents can exercise their legitimate right to go to work,' he said.

The law would require teachers to alert school officials 48 hours in advance if they plan to strike. The local authorities would be required to arrange care for pupils, but the central government would foot the bill, Mr Sarkozy said.

French citizens have 'the right to strike', but also 'the right to work', he said.

The strike, the third broad public sector strike since Mr Sarkozy took office a year ago, was another test of his resolve in his efforts to cut down France's large civil service to reduce Budget deficits and create more competition in the economy.

Some 40 per cent of teachers were on strike on Thursday, and 15 per cent of all public workers, according to the Public Service Ministry.

The strike action was to protest against the government's plan to cut 22,900 civil service jobs including 11,200 in education this September, and another 35,000 next year, mostly by not replacing retiring employees.

The government says the job cuts are necessary to rein in public spending and balance the Budget by 2012, in line with a French commitment to the European Union.

But the unions see a direct threat and students are worried about fewer teachers and less opportunity for good jobs.

Unions said the strike was a dress rehearsal for broader action planned for next Thursday, which is likely to halt rail and airline services.

They lashed out at Mr Sarkozy's proposal, saying he was seeking to pit teachers against parents.

'It is disappointing, exasperating and worrying,' said Mr Gilles Moindrot, head of teachers union SNUIPP.

In Paris, more than 50,000 civil servants, teachers, students and parents led by senior union leaders marched behind a banner that read: 'Together to defend and improve the public service,' according to organisers.

In all, some 200,000 people took part in protests in 142 cities, according to police, but union organisers said 300,000 had marched in the streets in defence of public sector jobs.

Clashes broke out during a march of 2,000 students in south-eastern Grenoble, as youths hurled cans and bottles at riot police who responded with tear gas.

Police blamed the violence on a small group of troublemakers.

Air traffic controllers in Marseille also joined the protest movement, causing a delay of between one and 1-1/2 hours to flights into and out of the southern city's airport, a spokesman for France's civil aviation authority said.

But the government stayed firm on its plans.

Reiterating the government's determination to pare down the education department, the biggest ministry employing some 1.2 million people, Education Minister Xavier Darcos said the key issue facing French education was the challenge of providing better education.

He said the protests, however large, would not change policy and did not answer the problems of French education today, which he called expensive and overstaffed, with falling class sizes.

AGENCE FRANCE-PRESSE, ASSOCIATED PRESS, NEW YORK TIMES