The Research Alliance for New York City Schools examined Department of Education (DOE) School Survey data from 2008-2010 to better understand the richness and complexities of the information elicited by the Survey from parents, students, and teachers. This report provides background information on the development of the NYC School Surveys during this time period and assesses the usefulness and appropriateness of measures derived from the survey and included in Progress Report grades. To do this, the authors first provided context about the School Survey's multiple purposes. Next, they outlined the survey development process, and gave information about similar large-scale survey efforts that informed NYC's survey measures and administration. They then presented a series of statistical tests used to examine whether the School Survey is useful and appropriate for describing the school learning environment, particularly whether it contributes meaningful information to Progress Report grades, and whether it identifies components of the learning environment that schools can target for improvement. Finally, the report outlines steps for improving the School Survey as a measure of the school environment, while also maintaining continuity in items and remaining a stable measure for School Progress Reports. This technical report is a companion to the brief, "Strengthening Assessments of School Climate: Lessons from the NYC School Survey". This report resents a detailed account of the statistical exploration of the reliability and validity of the NYC School Survey. [For the appendices to this technical report, "New York City School Survey 2008-2010: Assessing the Reliability and Validity of a Progress Report Measure. Technical Appendices," see ED560988. For the companion brief report, "Strengthening Assessments of School Climate: Lessons from the NYC School Survey. Brief," see ED560985.]