Educators in mainland China are increasingly concerned about promoting school students' social and emotional wellbeing. However, there has been little exchange of research between China and western countries about this topic. For example, questionnaires developed in the west have not been generally available to mainland Chinese researchers. We translated three existing wellbeing questionnaires into simplified Chinese characters and administered the questionnaires to 2756 students aged 10 to 15 attending 16 schools in Beijing. Results showed that students generally reported positive wellbeing, with only small proportions of students indicating languishing mental health. Comparisons between Chinese and Australian students of similar ages indicated that the Chinese students reported slightly higher wellbeing scores. However, as students in both countries grew older, their wellbeing scores became significantly lower. This study provides foundational information to underpin future work in Beijing schools to promote students' social and emotional wellbeing.