Advanced Placement (AP) Studio Art is an influential force in secondary art education as is evident in the 31,800 portfolios submitted for review in 2008. From the perspectives of a high school educator and AP Reader, this author has observed how the constraints of the AP program can be used to generate support for high school art programs and opportunities for large numbers of students to be seriously engaged with art learning. The AP portfolio can function as an "enabling constraint" for secondary art education. An enabling constraint creates structure and coherence by constraining a domain while simultaneously engendering unanticipated, imaginative, and divergent outcomes or responses. The AP Studio Art program also shapes student artmaking, primarily through the constraints of the portfolio assessment. The character of these constraints and whether they enable desirable outcomes are worth considering in the context of recurring questions about what constitutes foundational knowledge in studio art. The author concludes that the enabling constraints of AP Studio Art define a provocative and influential position in the ongoing discussions about assessment, foundational knowledge, and the changing character of artmaking.