There is a growing consensus that teacher evaluation in the United States is fundamentally broken. Few would argue that a system that tells 98 percent of teachers they are "satisfactory" benefits anyone--including teachers. The nation's collective failure to invest in high-quality professional feedback to teachers is inconsistent with decades of research reporting large disparities in student learning gains in different teachers' classrooms (even within the same schools). Many states and school districts are looking to reinvent the way they do teacher evaluation and feedback, and they want better tools. With the help of nearly 3,000 teacher-volunteers, the Measures of Effective Teaching (MET) project is evaluating alternative ways to provide valid and reliable feedback to teachers for professional development and improvement. In this report, the authors focus on the value of classroom observations. They test five different approaches to classroom observations. Each observation instrument is designed to do two things: (1) focus an observer's attention on specific aspects of teaching practice and (2) establish common evidentiary standards for each level of practice. In this report, the authors investigate the properties of the following five instruments: (1) Framework for Teaching (or FFT, developed by Charlotte Danielson of the Danielson Group); (2) Classroom Assessment Scoring System (or CLASS, developed by Robert Pianta, Karen La Paro, and Bridget Hamre at the University of Virginia); (3) Protocol for Language Arts Teaching Observations (or PLATO, developed by Pam Grossman at Stanford University); (4) Mathematical Quality of Instruction (or MQI, developed by Heather Hill of Harvard University); and (5) UTeach Teacher Observation Protocol (or UTOP, developed by Michael Marder and Candace Walkington at the University of Texas-Austin). Appended are: (1) Sample Restrictions Leading to Video Sample; and (2) Regression Coefficients Used for Criterion-Based Weighting. (This report was written with the assistance of Steve Cantrell, Jeff Archer, Sarah Buhayar, Kerri Kerr, Todd Kawakita, and David Parker. Contains 10 figures, 20 tables, and 45 footnotes.) [For related reports, see "Gathering Feedback for Teaching: Combining High-Quality Observations with Student Surveys and Achievement Gains. Policy and Practice Summary. MET Project" (ED540961) and "Gathering Feedback for Teaching: Combining High-Quality Observations with Student Surveys and Achievement Gains. Policy and Practice Brief. MET Project" (ED540962).]