ISSUE ADDRESSED: Health literacy is an important asset for adolescents to develop through engagement in schooling and curriculum. The few studies that have focused on teachers, health literacy pedagogies and assessment, show that teachers find it difficult to enhance students' critical health literacy levels and to measure students' health literacy knowledge and capabilities using valid models. The aim of this study was to develop a longer-term PD programme for secondary school teachers to enhance their ability to plan for critical health literacy learning and to co-design with teachers a curricular model for assessing health literacy. METHODS: Two face-to-face (F2F) PD sessions and two online PD sessions were scheduled with three participating specialist Health and Physical Education (HPE) teachers, seven HPE programmes were deductively analysed using Nutbeam's health literacy hierarchy and the Australian Curriculum: HPE outcomes and content. RESULTS: Analysis showed that interactive learning activities were dominant (64%), compared with functional (4%) and critical learning activities (4%). The co-designed curriculum model for measuring student health literacy was also developed for use in Australian schools. The resultant rubric is informed by Nutbeam's model, Broder et al.'s definition and Bloom's taxonomy. CONCLUSION: To our knowledge, this is the first ongoing teacher PD programme that has embedded co-design processes for teachers and researchers to design a curricular health literacy assessment model for Australian and international HPE programmes. SO WHAT?: The valid measurement and assessment of child and adolescent health literacy has largely been ignored in previous research. This study is the first attempt to co-design a curricular health literacy assessment for secondary schools that can be used by teachers and health professionals.