Three key aspects of the school environment are crucial for the prevention and management of social, emotional, and behavioural difficulties (SEBD) in schools. These include an adequate instructional environment, a supportive social-emotional climate, and a systematic process of identification and intervention. This paper addresses these critical aspects by presenting results from two studies in primary education in The Netherlands. According to teachers, one in six pupils in mainstream primary schools exhibits some kind of SEBD. Severe cases of aggressive behaviour or ADHD present the greatest difficulties for teachers. The focus in mainstream schools is on the provision of a supportive social-emotional environment and on the identification of SEBD, with little attention to an adequate instructional environment or consistent interventions. This paper describes a systematic approach to the prevention and early intervention of SEBD which will address this issue. ; peer-reviewed