The court in Bordeaux said 30-year-old Jeremy Forrest should be handed over to British authorities for running away with Megan Stammers.
"This is exactly the decision we were waiting for," said Forrest's French lawyer Daniel Lalanne.
French authorities now have three days to hand Forrest over to their British counterparts but his lawyer could not specify when he would be flown home.
Lalanne said the only charge his client could face in Britain was the kidnapping of a minor, specifically mentioned in an arrest warrant issued by Britain on September 25th.
French prosecutors said the minimum sentence for that offence was three years in Britain.
Forrest had on Tuesday agreed to be handed over to British authorities for questioning and his lawyer had said the teacher wanted the "full story to emerge".
Stammers was flown back to Britain on Saturday, a day after the pair were detained in the main shopping street of Bordeaux while on their way to a job interview.
The pair had boarded a cross-Channel ferry together on September 20th.
Security camera pictures were released of them holding hands and walking arm in arm aboard the ferry from Dover to the northern French port of Calais.
It later emerged they had initially travelled to Paris where they abandoned Forrest's car before travelling on to Bordeaux.
Their parents had appealed for them to get in touch but played down fears that the schoolgirl could be in any danger from the maths teacher.
There was never any suggestion that Stammers was taken by Forrest against her will, suggesting the British authorities may find it difficult to pursue kidnapping charges against him.
Under French law, a 15-year-old is not considered a minor in sexual terms, unlike in Britain, where the age of consent is 16.
The teacher, who plays in a rock band under the stage name Jeremy Ayre and has a wife aged 31, had hinted at a "moral dilemma" on his blog four months ago.