Three-quarters of Paris schools were disrupted by strikes Tuesday as teaching assistants took action against the reform.
They were joined by teachers, who started a two-day strike on Wednesday.
Primary and secondary school teachers, staff and parents are unhappy about controversial measures that add half a day to pupils' schedules.
In September 22 per cent of France's pupils began coming to school on Wednesdays, which was previously a day off, and the government plans to apply the reorganised schedule across the board next year.
The measure is meant to even out the workload of students, who had to spend long hours in after-school programs while their parents were at work.
But it's having the opposite effect, Bruno Mer of teachers' union FSU told RFI.
The FSU wants the law to be modified to allow more flexibility in its application and a round-table to discuss probmes that have arisen.
Education Minister Vincent Peillon insists that the reform is going well in 93.5 per cent of the 3,223 areas where it is in operation.
On Tuesday the mayors of 55 towns and cities declared that they would not implement the reform "in its current form" at the beginning of the next school year in autumn 2014.
Among the mayors, most of whom were on the right, was Jean-Claude Gaudin of France's second-biggest city, Marseille.
The right-wing UMP is to propose leaving mayors the choice as to whether to put the changes into practice.
Fifty-four mayors have signed a petition supporting the changes.