Jessica Lawson drowned in July 2015 after a swim in a lake with 23 other British children on a school trip. She died after the pontoon they were playing on capsized near Limoges in southwest central France.
The trial began Tuesday in nearby Tulle, attended by the child’s parents.
The suspects including the teachers from Hull, northeast England, and the lifeguard on duty at the time were charged with manslaughter caused by a “deliberate breach of safety or caution”.
The judges said on Wednesday there were too many elements in the case that were unclear including exactly when the child disappeared in the water.
The court also could not establish a link between the pontoon overturning and the schoolgirl’s death.
The local authority was also cleared of any role in the death.
It was the lifeguard who had found the missing child at the bottom of the lake (lac de la Triouzoune) on July 21 and she was airlifted to hospital. She died the next day.
The public prosecutor had requested a suspended sentence of three years for the teachers and the same for the lifeguard, who was 21 years old at the time, as well as a lifetime ban on doing similar work.
The suspects denied that they had failed to provide proper surveillance.
A lawyer for the schoolgirl’s family said they hoped the public prosecutor would appeal the court’s decision, pointing to many issues.
“A young girl of 12 disappeared, the pontoon was dangerous and there was an obvious lack of surveillance. Another court must hear this,” lawyer Eloi Chan told AFP.