Hamon described Le Pen’s attitude as “sickening” after she described French schools as “a daily nightmare,” so dangerous that pupils attend with “fear in their stomachs.”
Melenchon interrupted Le Pen as she was calling for boosted French-language teaching.
“How do you learn French, dear madam? By speaking it!” he said.
Some of the sharpest exchanges were about the place of religion in France.
Emmanuel Macron, the independent centrist leading polls with Le Pen, reacted heatedly when she accused him of being in favor of Muslim swimwear.
“I don’t need a ventriloquist,” he retorted.
He accused her of using religion to divide the French.
The televised evening debate involved the five candidates who are expected to be the largest vote-getters in the first round of the two-round vote.
The list of 11 candidates was finalized Saturday. The first round is set for April 23; the top two candidates go to a runoff May 7.