Classroom management underpins effective teaching and positively influences student learning outcomes. Proactive classroom management, which emphasises the prevention of problem behaviours, fits within a whole-school approach to positive behaviour support. In Queensland, many state schools are using Positive Behaviour for Learning as a framework for implementation of whole-school positive behaviour support. A number of key classroom management practices aligning with whole-school positive behaviour support have long been known, and are deemed to be evidence based. Yet, both locally and internationally, policy-makers, education systems, and the wider community are increasingly concerned by the disengagement from learning by students, the underuse of research-informed classroom management practices by teachers, and the level of problem behaviour in schools. This research set out to investigate the classroom management practices which Queensland state secondary school teachers reported using in their classrooms, and the perceived frequency of use of 14 practices drawn from the critical features of effective classroom management identified in a systematic literature review of evidence-based practices for classroom management (Simonsen, Fairbanks, Briesch, Myers, & Sugai, 2008). In addition, the research aimed to examine influences on teacher practice and to identify challenges facing secondary school teachers with an evidence-based approach to classroom management. The mixed-methods study used a two-phase design which first established broad trends in reported teacher implementation of classroom management practices, before a more in-depth exploration of themes in the second phase. In Phase 1, over 500 state secondary school teachers responded to a survey about their use of classroom management practices. Quantitative data from this phase were analysed using descriptive statistics and a Bayesian regression analysis. In Phase 2, semi-structured phone interviews were conducted with 26 of the surveyed teachers. A thematic analysis was then undertaken to identify key themes in relation to teacher use of classroom management practices and challenges to the consistent implementation of proactive, evidence-based classroom management practices in secondary schools. Overall findings showed that the practices which teachers reported using most frequently were setting expectations and boundaries, being consistent with routines, and delivering sanctions. Teachers also perceived that they were using 12 of the evidence-based practices at high frequency rates. Lower levels of use were reported across the entire sample for two of the practices: use of a classroom reward system and provision of a 4:1 acknowledgment to correction ratio. Teachers not working in a school implementing Positive Behaviour for Learning, or without good understanding of the principles of Positive Behaviour for Learning, reported comparatively lower levels of use of these two practices. Findings from the phone interviews indicated that teachers had only a general understanding of evidence-based practices for classroom management. In addition, several recurring themes in relation to challenges with consistent implementation of a proactive approach to classroom management were identified. In particular, inadequate pre-service preparation, poor teacher induction processes, and limited access to ongoing professional development were identified as challenges. School policies and procedures which focused on punishment of problem behaviour, lack of classroom management support from administration, undifferentiated curriculum, student disengagement, and inadequate resourcing also emerged as implementation barriers. Findings from this study have a number of important implications for policy, practice, and future research. There is an urgent need to reshape the discourse around behaviour in Queensland schools to promote positive behaviour support and underscore the importance of proactive classroom management for improved student outcomes. There is also a clear need for improvements to pre-service teacher training, new teacher induction processes, and access to quality professional development in classroom management. Importantly, this research confirms the need for implementation support to be provided to schools, especially through provision of ongoing coaching to build teacher knowledge and capability in use of proactive classroom management practices. This was the first Australian study to examine teacher-reported use of the evidence-based practices for classroom management which align with a whole-school framework for positive behaviour support. Future Australian research is needed to explore more fully how Positive Behaviour for Learning is being implemented in schools.