School pupils are expected to be back at the barricades in France on Tuesday for the biggest day of protests so-far, after officers made more that 5,000 in clashes across the country last week.

Hundreds of people have been injured in the demonstrations, and one 15-year-old boy had his hand blown off outside a school in Lens, in northern France, on Monday, the state representative for Pas-de-Calais said.

Of the 5,000 arrested last week, 85% were minors, France’s interior minister Laurent Nuñez said.

The influential CGT labor union has urged workers to join the demonstrations on Tuesday, with thousands of trade unionists, teachers, and parents’ groups expected to march in support.

Protests first erupted in the Paris region in mid-September, with teachers and students mobilising against a lack of staff at a lycée, or high school, in Creteil, in the southeastern outskirts of the French capital.

From there, class strikes, blockades and demonstrations spread to other Paris suburbs and then nationwide, with protests erupting in high schools of smaller towns.

Pupils are focused on what they say are inequalities in the school system, such as differences in teaching, facilities and opportunities for students in disadvantaged neighborhoods compared to elsewhere.

Long hours have also been frequently cited as a protest point, as school often starts at 8am and can last until the early evening. French high schoolers’ compulsory school hours are among the highest in Europe, according to European Union figures.