The Association of Secondary Teachers in Ireland has claimed that education is suffering because of drug and alcohol abuse among students.
The ASTI president, Mr Pat Cahill, said hangovers, poor concentration and depression were now evident in the classroom. He was commenting after a UN survey showed young Irish people to be the biggest abusers in Europe of amphetamines and ecstasy.
The report by the UN Office on Drugs and Crime said levels of speed abuse were more than five times higher in Ireland than in most other European countries.
However, the Minister of State with responsibility for the National Drugs Strategy, Mr Noel Ahern, has urged caution, saying the figures were primarily based on "a limited survey and are not necessarily comparable with data for other countries contained in the report".
Mr Cahill linked the trend with secondary students having more disposable income. "The school learning environment is suffering as a result of students being unable to engage because of the after-effects of drugs and alcohol," he said.
"Drug abuse militates against learning and progress at school as young people try to cope with hangovers, reduced levels of concentration and feelings of depression. Such side effects have a significant effect on academic progress and in some instances can increase a student's chances of dropping out of school."
Mr Cahill said there must be Government initiatives to support the efforts of schools and teachers. Reducing class sizes would help to ensure the needs of high-risk students were identified, he said. Students must also have adequate access to specialist teachers such as guidance counsellors.
The president of the Union of Secondary School Students, Mr Daire Hickey, said he was not surprised by the UN report. The level of drug use in Ireland was at "an amazing level".
Mr Hickey called for school facilities to be opened after-hours. "Often schools have great pitches and halls which could be used for young people to play sports and as an alternative to drug-taking. We have got to put more money into the youth sector."
Bored students were vulnerable students "and Irish students are certainly some of the most bored in Europe", he said. Taking drugs often cost less than other activities - the cost of leisure activities had increased dramatically in recent years, he added.
Mr Clive Burkette of the Coolmine Therapeutic Community, which works with drug abusers, said greater resources should be made available to the Garda and Customs to tackle drug-importation. "For every person busted and every consignment seized, there are three or four which escape the authorities," he said.
A spokeswoman for the Department of Health said it had run several initiatives to tackle drug-abuse and a drug-awareness campaign was launched last year.
Mr Ahern also said the data used was several years old. The Government, through the National Advisory Committee on Drugs, had commissioned an all-Ireland population study on drug use last year which would be published on Monday. It would give a more accurate picture of drug use, he said. "We expect that the figures will show Ireland to be more in line with international norms."