Teenage boys will be tempted to experiment and it is a cause of great concern that such information should be on the net

Jeremy Poulter, school spokesman

They had discovered an internet site which gives details on how to cook up an ecstasy substitute.

All four have made a good recovery, but Glenalmond has a clear policy on drugs and immediately expelled the pupils.

School spokesman Jeremy Poulter said: "Teenage boys will be tempted to experiment and it is a cause of great concern that such information should be on the net."

He said that the recipe showed the boys how to produce an ecstasy-type substance from easily available ingredients.

"They had experimented with it. The effects became obvious very quickly and pupils immediately alerted the college medical staff.

Drugs policy

"Mercifully the boys are safe and well and will not suffer any long-term consequences as a result.

"However, we have a clear policy on the taking of drugs and none of the boys will be returning to the college," he said.

Glenalmond College was recently named as one of Scotland's top five schools for GCSE and A level results.

Former pupils include Harry Potter star Robbie Coltrane and former Scotland rugby captain David Sole.