French school principals are appealing for protection after several school administrators have been injured by youth protesting against labor reforms.

High school and college students are playing a prominent role in weeks of protests over a bill to relax the work week and make layoffs easier.

The SNPDEN school administrators' union said the latest violence hit Voltaire High School in Paris on Thursday, leaving two deputy principals lightly injured after being punched and hit by gravel.

SNPDEN deputy chief Michel Richard said one school's principal suffered three fractured ribs when a protester jumped on her, another was punched in the face and a third was bruised by garbage cans piled on by protesters.

He says "we ask the state to intervene as fast as possible."