Assessments and examinations play a critical role in certifying student achievement in secondary education. Prompted by concerns about the negative effects of examinations on curriculum, teaching and learning, elements of School-Based Assessment (SBA) have been introduced into certification systems, sometimes modelled on practice in other jurisdictions. This case study investigates factors influencing efforts to introduce SBA in lower secondary education in the Republic of Ireland and reactions from the main stakeholders. Policymakers' perspectives were informed by national consultations, results of international assessments, trends towards skills-based curricula and practices in relation to SBA as part of high-stakes assessment internationally. Despite broad enthusiasm for the reforms from most stakeholders, teachers remained opposed. A series of compromise proposals shifted the reforms far from their intended nature, leaving in place a dual system of assessment that incorporates continued centralised examining by the state along with some non-certified SBA by teachers. The efficacy of this solution in relation to the original aims of the reform remains to be seen. The analysis explores relevant substantive and methodological issues. The complex interplay between international, national and very local influences on policy implementation is highlighted, suggesting the need for due diligence in anticipating and managing stakeholder responses to reform initiatives. Readers' attention is also drawn to the intricacy of undertaking qualitative case study inquiry and the need for awareness in relation to possible alternative interpretations of data.