Image caption Good school sport should be "enjoyed and played in the right spirit"

Prep school parents are putting their children under too much pressure at sports events, a head teacher warns.

Leonard Blom, a former international cyclist, wants parents to "stop yelling" and "control their emotions".

He says parents are forgetting children play sport for their own enjoyment, not that of their parents.

Sports' governing bodies share the wider concerns, with the FA saying a "touchline manager" might be needed to keep parent spectators under control.

Mr Blom's is the head of St Aubyn's preparatory school in north London, and has written a guide for parents on how to encourage their children appropriately at school sports events.

Writing in the magazine for the Independent Association of Prep Schools, Attain, he highlights the antics of several badly behaved parents he has witnessed.

He describes one father getting so involved in a rugby match that he intervened in the game, by taking a quick throw-in when the ball went out of play, and a mother who "collapsed in a heap" at a swimming gala, after pacing up and down poolside shouting at her daughter.

Mr Blom adds the girl "never excelled at swimming".

"Sometimes we need to take a step back and not get too emotionally involved," he says.

"The real winners in sport - and in life itself - are those who persevere and behave with dignity, whether they win or lose."

Mr Blom argues that the one of the main goals of school sport is to "develop good sportsmanship, and learning to treat teammates, opponents, coaches and officials with respect".

They are themes sport administrators take very seriously.

The Football Association's Respect campaign, for example, aims to promote those values throughout the game, and the FA believes negative comments and behaviour by parents can put a child off the game for life.

In 2012 it gave £200,000 to provide "Respect Barriers" to schools and clubs - designed to keep parents from encroaching on the pitch during matches.

Perhaps the key piece of advice from Mr Blom to parents is to keep things in perspective. "It is not the World Cup," he says, "it is a prep school game. Treat it as such."