This research study has sought to examine and evaluate how the presence of children with Attention Deficit Hyperactivity Disorder (ADHD) impacts upon the educational and behavioural climate of the mainstream classroom. It also addresses the effectiveness of a range of approaches to the management of such children with ADHD in the classroom. These approaches include medical intervention in the form of a prescribed drug and the use of a behaviour management strategy. The research focused on a sample of primary schools in Northern Ireland. Analysis of the information demonstrated that children with ADHD do impact upon the mainstream classroom and usually in a negative manner. The study found that a variety of approaches could be effective in managing ADHD children. In some cases the best solution was a combination of methods, generally involving the use of a prescribed medication alongside a behavioural management strategy. Results showed that the most effective form of behavioural management was a positive behaviour strategy or time out.