For decades, school districts across the Nation have been pressured to close the achievement gap among students and have been held accountable for student outcomes. According to past researchers, there is a need to revise completely the teacher evaluation practices used in the 1980s and 1990s to better measure teacher effectiveness. More recently, researchers have recommended that educational stakeholders identify a theory of action to address lagging student performance because of ineffective teaching. With the changing trends in education, the identification and retention of effective teachers have become a heated topic in education, although the teacher evaluation process held little value historically. Despite reform efforts and major policy changes, a consistent question that has reverberated throughout the research has been "Why it is so hard to define effective teaching?" To that end, the catalyst for this study was the quest for increased accountability for everyone who is responsible for providing all students in a Kindergarten-Grade 12 (K-12) setting with a quality education. Therefore, the researcher examined the relationship between teachers' observation of practice scores and teachers' effectiveness scores as measured by Tennessee Value-Added Assessment System (TVAAS). Teachers' individual TVAAS scores and observation scores for the 2013-2014, 2014-2015, and 2015-2016 school years were analyzed as part of this quantitative, empirical study. The researcher found that a significant relationship existed between teachers' mean observation scores and the student growth scores on the TVAAS. The researcher also suggested that for every point higher that teachers were rated on their observation scores, their student growth score on the TVAAS increased by nine tenths of a point. Furthermore, the results indicate that teachers' observations made a positive impact on improving a teacher's effectiveness score as measured by student growth on the TVAAS. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]