Despite continuing concerns about disruptive behaviour in schools and how best to manage it, it is comforting to note that progress is being made on many fronts. In recent years, policy makers and educators have come closer to agreement about what constitutes ‘best practice’ in behaviour management at the system and school level. There is a growing recognition that whole school and whole school community responses to student behaviour are the most efficient and effective ways of both encouraging good behaviour and responding to unacceptable behaviour. One model of whole school behaviour management and support, namely Positive Behaviour Support (PBS) is rapidly becoming the preferred approach in Australian schools. PBS in its various designations, for example, School Wide Positive Behaviour Support (SWPBS) and Positive Behaviour for Learning (PBSL) is now being widely trialled and/or adopted in states such as Queensland and New South Wales. Central to PBS is the shift in emphasis from attending to and correcting problem behaviour, to one of increased attention given to good behaviour, both its recognition and its reward. The celebration of good behaviour is now a feature of the operations of many schools, both PBS and non PBS and this change in focus appears to be unproblematic. Less is known about what is happening at the classroom level. The literature on PBS calls for a high ratio of positive to negative teacher-student interactions, as high as five to one (Sugai, Horner & Todd, 2000). Decades of research on classroom interaction would suggest that such a ratio is unusual and to achieve it would require a significant change in teacher behaviour. This paper explores the challenges teachers working within a PBS environment face as they strive to meet recommended targets for the acknowledgement of positive student behaviour. The particular focus of the paper is on the ratio of positive to negative interactions for students whose behaviour in the classroom is often problematic. More often than not the ratio of positive to negative interactions for these students is the reverse of that for cooperating students and far less than what might be hoped for in a PBS classroom. Behaviour correction is a necessary part of what teachers do in the classroom, but getting the balance between acknowledgement and correction right is important to ensure that attention to good behaviour is what characterises individual student and overall classroom interactions. This paper looks at ways teachers can more readily achieve the balance even when working with difficult and challenging students. The paper addresses what can best be described as ‘missed opportunities’ for acknowledgement, those occasions, more numerous than teachers often believe, when problem behaviour students are on task and well behaved.