Andy Mackillop from West Mercia police praised the school for the way it involved the local police. Teachers noticed odd behaviour among some Year 10 pupils just before Christmas and at the start of this term.
Fighting broke out between some boys who were trying to prevent others from selling the girls LSD "tabs" - small squares of paper containing a micro dot of the liquid which is then dissolved on the tongue, costing about Pounds 3.
"Because they called us in at an early stage we nipped the problem in the bud. It was just a small group of young people who were experimenting; but we are taking the three who allegedly supplied it more seriously."
The Health Education Authority is planning to start an education programme focusing on LSD, Ecstasy and speed later this month. Young people will be encouraged to use the HEA's helpline on 0800 776600.