Brief Behavioral Teacher Training for Behavioral Difficulties

The goal of this two-armed randomized controlled trial is to investigate the effectiveness of a new, individually tailored, brief behavioral training for teachers of children with behavioral difficulties at school. The main questions the study aims to answer are: * Does the brief teacher training reduce the severity of four daily rated target behaviors in specific classroom situations compared to practice as usual (PAU) on the short term? * Does the brief teacher training program reduce the severity of the same four daily rated target behaviors in other classroom situations, behavioral difficulties of the child at school and at home, and the impairment of the child in the school situation and reduce the number of behavioral difficulties of the child at school judged as troublesome by the teacher, and improve the teacher-student relationship quality, teachers' sense of efficacy, and teachers' behavior management strategies compared to practice as usual (PAU) on the short term? * Are short-term improvements maintained at 3 months follow-up? Teachers will be randomly assigned (simple randomization) to (a) three sessions of brief teacher training with PAU, or (b) PAU only. The brief teacher training provides teachers with individually tailored stimulus control and contingency management techniques to treat children's behavioral difficulties in two (bi)weekly training sessions of two hours and a third session of one hour in which the training will be evaluated and maintenance training will be provided. PAU may include any support or treatment as regularly provided by mental health care centers, schools, school collaborations and/or other organizations, except from pharmacological treatment for children's behavioral difficulties and/or behavioral teacher training/support. PAU can also imply that there is no support or treatment.