Each can of Red Bull contains the same caffeine as a cup of coffee
A Surrey school has banned its pupils from drinking high-energy drinks because of their impact on behaviour.
Oxted School said it was increasingly concerned about the number of pupils consuming the beverages.
Head teacher Guy Nelson told parents he thought it was a "sensible and reasonable" step to take.
A spokesman for the energy drink, Red Bull, said it does not recommend its beverages to caffeine-sensitive individuals, including children.
Mr Nelson said he was "increasingly concerned" about the number of pupils drinking high-energy drinks including Red Bull on their way to school.
In a letter to parents, he said: "This has marked behaviour impact on the students and in our view is in contradiction to our 'healthy schools' policy."
He added: "I am sorry if this seems a draconian new school rule but we are convinced that this is both a sensible and reasonable step to take."
The company Red Bull said its drinks contain 80mg of caffeine, the same amount as a cup of coffee.
In October 2009 a school in East Sussex asked two local shops not to sell high-energy drinks to pupils.
Cardinal Newman School in Hove also feared the drinks had an impact on children's behaviour in class.