The antipathy of federal and state courts toward equal protection arguments in lawsuits challenging the public funding of education have forced education activists to search for alternative doctrinal hooks as they continue to seek reform in states’ funding and management of schools. These activists have turned to state constitutions’ education clauses, which impose duties on state governments to provide an “adequate” education for all children in the state. However, the art of defining and measuring an “adequate” education has advanced little beyond its state in 1973, when Justice Thurgood Marshall found the term unhelpful. In this Note, Josh Kagan surveys various means of defining and measuring adequacy used by state courts, including the use of existing legislative or executive standards, the use of future legislative or executive standards, a variety of educational outputs (such as standardized test scores), and educational inputs (such as quality of teachers, curricula, or school buildings). Applying scholars’ theories of state constitutional interpretation and the history of state education clauses, Kagan argues that state courts should be aggressive in their use of educational inputs to define and measure educational adequacy. Unique factors of state governmental structure justify state court involvement in education policy questions that federal courts would consider inappropriate. These factors, coupled with the history of state education clauses, enable state courts to draw on a wide set of historical and current sources to define educational inputs required by state constitutions, and provide jurisprudential guidelines for this necessarily policy-laden analysis. Such an approach also encourages education activists to seek remedies other than reform to school financing systems; instead, activists can target states’ provision of particular educational inputs.