The body of Agnès Morin was discovered on Friday, two days after she disappeared while in a forest close to the fee-paying Cévenol school where she was a pupil.
It has been revealed that the 17-year-old boy who confessed to raping and murdering her also attacked another girl in similar circumstances a year earlier.
The victim of the earlier attack survived and the boy was imprisoned for four months. On his release he was transferred to the Cévenol school but authorities there claim they were not aware of the exact nature of his crime.
Prime minister François Fillon called an emergency meeting of his justice, interior and health ministers on Monday afternoon to discuss "possible failings in the chain of justice."
Justice minister Michel Mercier told reporters after the meeting that there needed to be better structures to "evaluate the danger" in serious cases.
Interior minister Claude Guéant appeared on the TF1 nightly news programme to announce that steps to reform youth justice would be a "priority" after the elections planned for June 2012.
He rejected the call of far-right leader Marine Le Pen for a referendum on reintroducing the death penalty to France following the murder.
"France is proud to have abolished the death penalty and it's sickening to put that back into play. I hope that the French will not listen to these populist demands," he said.
Le Pen had earlier told radio station Europe 1 that "those who kill our children should risk their own skin."
She promised that, if elected in next year's presidential elections, she would hold "a referendum to ask the French people to make the choice between the death penalty and life imprisonment."