A school has banned energy drinks claiming they have a detrimental effect on pupils' health and ability to study.

The Angus school has informed all parents that high caffeine drinks will not be allowed after some pupils were drinking them for breakfast, and one pupil even ended up in hospital.

Forfar Academy head teacher Melvyn Lynch said a small minority of pupils as young as 11 were suffering behavioural problems after getting addicted to energy drinks.

He told STV News: "Unfortunately now a lot of youngsters have started drinking these, even at primary school age.

"The amount of caffeine has quite an alarmingly detrimental effect on young people's systems.

"A can of Monster is not going to make you into a calm, obedient child.

"We are dealing with children becoming very agitated, irritable and displaying sometimes quite challenging and combatant behaviour.

"For a minority of children we could be talking about some form of addiction. There has become a bit of a culture in it.

"Some of the kids are saying they get a hit from it, not like drinking something sugary like cola.

"I will sometimes see children coming in drinking these things in the morning."

In his letter to parents and carers, Mr Lynch informed them issues with energy drinks, including recent exclusions, would result in them being banned from the school premises from Tuesday.

He said in one of the more serious incidents a child who bought and drank ten mini cans of an energy drink while on a school trip to France ended up spending the night in hospital as a result.

In the latter to parent Mr Lynch said: "These drinks, such as Rock Star and Monster, pose a health risk to our young people due to the ingredients they contain.

"Energy drinks contain high levels of caffeine and sugar. In a small 250ml can there is typically 80mg of caffeine.

"This is the same as three cans of coke or a small mug of coffee.

"There is also very often hidden caffeine content from an ingredient called Guarana which can greatly increase the actual amount of caffeine in each drink.

"The amount of sugar in each energy drink is also a real concern as large cans contain as much as 60g of sugar - that's 15 teaspoons of sugar."

Mr Lynch said while children will not be excluded if they are caught with these drinks, the ban was about "changing behaviour" of the risks involved.

He said energy drinks should be aimed at adult customers and said a change in marketing could help tackle the issue.

Both Monster and Rockstar have been contacted for comment.