The Secondary School Principals Association says a binge-drinking culture among some young people is making itself felt in Monday morning classrooms.
Association president Patrick Walsh says it is a great disappointment the Government did not raise the price of alcohol or do away with advertising targetting young people.
He says teachers on Monday mornings have to deal with students who are lethargic, hungover, or still drunk after drinking solidly during the weekend.
Mr Walsh says parents should take responsibility for what their children are doing because schools can not always solve teen issues.