This was a non-experimental, mixed methods study to research the different ways in which the Marzano casual teacher evaluation system was implemented in 25 school districts in the state of Florida during the 2012-2013 school year. Based on seven implementation variables, the teacher evaluation systems were compared to the implementation model and research-based best practice. The researcher then sought to determine what relationships may or may not exist in teacher performance ratings between districts that followed the research-based implementation model and districts that did not. Two stated purposes of the Marzano causal teacher evaluation system were to improve the accuracy of teacher performance ratings and to improve the accuracy of feedback provided to teachers. Variation in implementation may possibly occur among school districts. To date no research has been conducted to analyze how variations in implementation may relate to teacher performance ratings. The purpose of this study was to provide data to support best-practice in the implementation of the Marzano causal teacher evaluation system and to guide instructional leaders on the implementation of this evaluation system. The researcher also sought to ensure the Marzano causal teacher evaluation system provides both accurate teacher feedback and accurate teacher evaluations. Data was collected from the Florida Department of Education published reports and information. School district implementation plans were gathered from state submitted documentation. Implementation plans were analyzed and read. Data was collected on a data collection sheet and then analyzed in SPSS using a crosstab Chi square test to determine if a statistically significant relationships existed between districts that followed the research-based implementation model and districts that did not. It was determined that implementation of the Marzano causal evaluation system varies widely. In six out of the seven implementation variables, it was determined that there were statistically significant relationships in teacher evaluation scores between districts that followed the research-based implementation variables and districts that did not. Further research should include validity and reliability studies on the Marzano causal evaluation system. Research should continue to analyze different ways in which the Marzano causal evaluation system is implemented, and what relationship there is between implementation and teacher performance ratings. Research should be conducted to analyze the effectiveness of feedback provided to teachers through the Marzano causal teacher evaluation system. This research indicates that the Marzano causal teacher evaluation system should be used following research based best-practice and how it is intended to be used. The research in this study shows that when implementation variables are altered in the Marzano causal teacher evaluation system, teacher performance ratings may become inaccurate. Based on misunderstandings of the Marzano causal evaluation system, it is recommended school leaders receive additional training on the understanding and implementation of the Marzano casual teacher evaluation system.