Efforts to improve student performance on high-stakes assessments in mathematics place teachers in the epicenter of multiple reform expectations. While studies have documented how teachers implement single reforms, very little is known about teachers' implementation processes when multiple expectations are imposed. With a focus on how elements in the setting affect teachers' decision- making regarding their implementation of instructional initiatives, this study explored how five teachers from one mathematics department at a comprehensive urban high school enacted and perceived mandates (initiatives with high external accountability), and other reforms (initiatives with perceived low or no accountability). Using multi-case study methodology and various data sources, the implementation processes revealed that multiple initiatives did not result in integrated reforms. Participants made decisions about each initiative independently and holistically rather than filtering out elements from multiple initiatives and blending them into their current instructional practice. The demographic surveys triangulated data about teachers' experiences and tendencies towards adopting new ideas into practice. The ecocultural teacher interviews situated teaching practices within the current setting and the group interviews showed how collaboration triggered responses, learning, and implementation. Analyzed lesson observations characterized the enactments of reform, and the reflection interviews uncovered teachers' perceptions of the reforms. Data analyzed qualitatively using within and cross-case approaches showed similar decision-making and implementation processes among the participants. Results showed that mandates themselves did not guarantee the adoption of reforms; rather, organization for enactment occurred when teachers perceived the context of each mandate aligned to their beliefs about teaching. Specifically, determining factors of teachers' decisions to adopt or reject each reform depended on their perception of 1) the reform's alignment to their pedagogy and content, 2) the importance or relevance of the mandate, 3) external pressure and accountability and 4) how students would react to the reform. Common planning time and teacher professional teams supported implementation while student behavior and lack of content readiness negatively affected teachers' willingness or ability to enact reforms. Recommendations to support implementation include developing structures for sustained peer collaboration and providing ongoing, on-site training to encourage and support risk-taking, and the integration of multiple expectations