French teachers are staging their second strike this week in protest at government decentralisation plans and pension reform.
Teachers have had several strikes in recent weeks
Education Ministry sources reported that about a quarter of France's 800,000 teachers were on strike, leading to some classroom closures.
Hundreds demonstrated in major cities including Paris, where participants joined hands in a human chain around the ministry building.
Teachers have led the way in nationwide strikes by public sector workers in recent weeks over pension reforms which would see people's working lives being prolonged.
They also fear job cuts and plans to hand over some responsibility for school staff to local authorities, which they believe will disrupt the education system.
Deputy Education Minister Xavier Darcos said the government might compromise on decentralisation plans.
"If the government considers the plan should be modified in this way or another, it will do it," he told French television.
But on Tuesday Education Minister Luc Ferry warned that he would not tolerate disruption of the forthcoming end-of-year exams.
Some hardline teachers have threatened an exam boycott, and sessions have already been affected in the southern cities of Toulouse and Perpignan.
Mr Ferry said he would not be deterred by street protests and had various legal means at his disposal to deal with the situation.
Meanwhile some French unions have been outlining strike plans for the near future.
Hundreds of thousands are expected to join a national demonstration in Paris on Sunday, with more air and municipal transport strikes planned in the following two weeks.
Public sector workers caused some disruption in strikes on Monday, just days after the government split the labour movement by making a deal with more moderate unions.
The unions are still hoping for a repeat of the mass demonstrations against pension reform in 1995 which brought down the conservative government of Alain Juppe.
The current government, however, says it is determined to weather the storm.