From a developmental construct validity perspective, this study examines motivation and engagement across elementary school, high school, and university/college, with particular focus on the Motivation and Engagement Scale (comprising adaptive, impeding/maladaptive, and maladaptive factors). Findings demonstrated developmental construct validity across the three distinct educational stages in terms of goodfitting first- and higher order factors, invariance of factor structure across gender and age, and a pattern of correlations with cognate constructs (e.g., homework completion, academic buoyancy, class participation) consistent with predictions. Notwithstanding the predominantly parallel findings, there was also notable distinctiveness, primarily in terms of mean-level effects, such that elementary school students were generally more motivated and engaged than university/college students who in turn were more motivated and engaged than high school students. Implications for motivation and engagement measurement and theory, research in the psychoeducational domain, and the subsequent potential for performance profiling across the academic life span are discussed.