The American Supreme Court has given high schools the right to test all children who take part in extra-curricular activities for drugs.

Before now, drugs tests were only permitted for school athletes. But the court ruling extends this principle to other competitive and team activities, from cheer-leading to chess.

This policy reasonably serves the school district's important interest in detecting and preventing drug use

Justice Clarence Thomas

The judges said the issue they were debating was a serious national problem, and that testing was a justifiable way of addressing schools' concerns over drug abuse.

But critics say the ruling will lead to less involvement in after-school activities and more drug problems among the young.

Oklahoma test case

The case before the judges involved a former Oklahoma high school honours student who competed on a quiz team and sang in the choir.

Lindsey Earls, who described herself as a goody-two-shoes, tested negative for drugs but decided to sue her school.

Critics say the ruling will lead to more not less drug abuse

By a 5-4 vote, Supreme Court judges upheld the school's programme, which requires students who want to take part in after-school activities to submit to random urinalysis.

Students are tested at the start of the school year and then randomly at other times throughout the year.

A student who refuses to take the test or who tests positive more than twice cannot take part in competition for the rest of the school year.

"Because this policy reasonably serves the school district's important interest in detecting and preventing drug use among its students, we hold that it is constitutional," said Justice Clarence Thomas.

One of the judges said that school drugs tests offered adolescents an easy reason to decline the pressure to experiment with drugs, since they could tell friends that they intended to take part in after-school activities.

But the American civil liberties union said the ruling was counter-productive - reducing involvement in school activities and leading to more children being on the streets where they would be more likely to take drugs.