Two Dublin fee-paying schools have denied they operate a "mandatory" drug-testing policy.
St Andrew's College, Booterstown, and Sutton Park School said they did not test students for drugs as part of a mandatory programme as this would be highly inappropriate.
In a small number of cases, if the schools had evidence or strong suspicions of drug-taking, they might test students, but only after getting the consent of parents.
Mr Arthur Godsil, principal of St Andrew's, said the school had tested about a dozen students over the last three years. The tests were carried out because the school had "good cause" to think the students were using cannabis.
St Andrew's had been doing this since 1999 and its policy was well known to parents and the school community. He said the vast majority of students passed through the school without being tested. Details of this were posted on the school's website.
Mr Tony Blackman, principal of Sutton Park School, strongly denied the school operated a mandatory policy and said reports which suggested so were wrong.
He said students believed to be using drugs were tested, but there was no general policy of testing the school's 270 pupils. Parents were aware of the policy and their consent was needed for any testing.
Mr Blackman said the school tried to work with students caught taking cannabis and expulsion was a last resort.
Both schools were annoyed at reports which suggested they had introduced a mandatory regime. Few schools in Ireland would be prepared to impose such a policy. Apart from legal difficulties, such a move would be deeply unpopular with parents.
Principals contacted by The Irish Times yesterday said they had no mandatory testing policy. Most said school rules made it clear drug-taking would not be tolerated under any circumstances. If drugs were abused by a small number of students, it was almost always cannabis, they said.
The Department of Education said it was up to schools how they handled the drugs issue. A spokeswoman for the Minister for Education, Mr Dempsey, said substance misuse was a serious reality which confronted many homes, schools and communities on a daily basis.
Young people were particularly vulnerable and the Government was determined to take the necessary steps to protect them from the dangers of substance abuse.