He said the three were from a high school in Concarneau, in the western Brittany region.
Local radio France Bleu said around a dozen students were on the bridge at the time of the attack, and that the three injured were taken to hospital.
A local newspaper, Le Telegramme, also said the students were on the bridge when they were hit by the car, quoting another student who said the force of the impact threw one of them onto the bonnet of the vehicle.