At the University Hospital of Leuven a toolkit for school behaviour modification in children with ADHD has been developed and piloted. This is an instrument for teachers to systematically target specific behaviours in the classroom and the playground with the ultimate goal of improving school ADHD behaviours and reducing oppositionality. Teachers will identify the behaviours which are most challenging and apply a series of levels of intervention with increasing intensity of monitoring, feedback and training. The effect of a three month application of the toolkit will be evaluated compared to a waiting list control group. Outcome measures will include measures of ADHD behaviours, oppositional defiant behaviour, teacher attitudes towards ADHD, teacher-child relationship and child self-esteem.