Limited empirical evidence is available regarding the uptake and effectiveness of school-based mental health and wellbeing programs implemented in Australian schools. This study aimed to characterise the delivery of programs in primary (elementary) schools across New South Wales, Australia, and to assess this information against published ratings of program effectiveness. Delivery of programs in four health-promoting domains--creating a positive school community; teaching social and emotional skills; engaging the parent community; and supporting students experiencing mental health difficulties--were reported by 597 school principals/leaders via online survey. Although three quarters of principals reported implementing at least one program, many of these programs were supported by little or no evidence of effectiveness. There was also variability in the use of evidence-based programs across the four domains. Findings indicate a need to provide educators with improved support to identify, implement, and evaluate effective evidenced-based programs that promote student mental health.