Existing measures of belonging in schools do not explicitly elevate the contextual and cultural insights of the educators and students they were designed to assess. Our study addresses this shortcoming through the co-creation of an Opportunities to Belong survey measure for urban middle schoolers. The tool was developed in partnership with practicing educators and normed around Black and Latinx students (N = 225). Results of a multilevel confirmatory factor analysis revealed strong evidence for single factor structure. A within-persons multilevel model revealed that shifts in opportunities to belong predicted fluctuations in student engagement across different academic courses. Implications are discussed.