The need for a new measure of social-emotional wellbeing for children 6-12 years emerged in our collaboration with schools and community agencies in a disadvantaged region of Brisbane, Australia. Our search for an age-appropriate medium led us to develop Clowning Around, a computer game generating data which was assessed for validity and reliability in Study 1 (n=3,461), revealing four wellbeing factors with satisfactory properties. The imperative to support autonomous use at scale led to development of the Rumble’s Quest user management system and game app, incorporating a slightly modified version of the measure. Reassessment of the factor structure (Study 2: n=4,333) supported Study 1 results but extended subfactors to five: Educational Wellbeing, Social Wellbeing, Emotional Wellbeing, Protective Contexts, Behavior Regulation. The measure exhibits sound convergent and concurrent validity and is a reliable and practical tool for service planning, evaluation, and monitoring child wellbeing trends. Methodology is in the paper. 4 data files: 1. N=3461 Clowning Around factor analysis 2. Convergent validation data for CA N=1822 3. Test-retest N=347 for CA 4. Rumble’s Quest factor analysis N=4333