The purpose of this study was to examine the relationship between the collective efficacy of teachers and student achievement at economically disadvantaged middle school campuses. Schools of today are expected to show continuous improvement in student achievement from year to year, regardless of the students' family background, ethnicity, or socioeconomic status. In spite of mandates, many middle school campuses that serve economically disadvantaged students in the state of Texas fail to meet minimal standards (Academically Acceptable) established by the Texas Education Agency (TEA), while other campuses serving the same population of students (economically disadvantaged) received the state's highest rating (Exemplary). The population of the study consisted of Texas campuses that served economically disadvantaged students and received a campus rating of Exemplary or Academically Unacceptable for two consecutive years, according to TEA. Ratings for the 2007-2008 and 2008-2009 school year were utilized to select campuses for the study. A total of six campuses participated in the study. Data for the study was collected utilizing the 12-item Collective Efficacy Scale (Short Form) created by Goddard (2002). From the analysis of data, it was shown that significant differences exist between the collective efficacy of teachers from Exemplary and Academically Unacceptable campuses. It was also discovered that the Assessment of Teaching Competence (GC) and Analysis of Teaching Task (TA) is higher for teachers from Exemplary campuses versus that of teachers from Academically Unacceptable campuses. The findings of this study were supported by the review of literature. These finding add to the review of literature on the effect of teachers' collective efficacy on student achievement. The quantitative findings presented in the study provide further knowledge on the relationship between collective efficacy and student achievement. This study has found that the collective efficacy of a campus can influence student achievement at the middle school level. The study was intended to provide information that could be utilized by administrators of public schools to assist in creating campuses that have high collective efficacy. Specifically, the findings of this study should be of interest to low performing campuses across the state of Texas that struggle to meet the minimal state accountability standards. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]