http://ies.ed.gov  The Federal Government operates multiple education research sites through the Institute of Education Sciences, “the nation’s engine for education research, evaluation, assessment, development and statistics.”  Under the IES you will find several additional national programs, including:

http://ies.ed.gov/ncer  The National Center for Education Research.
http://nces.ed.gov  The National Center for Education Statistics
http://ies.ed.gov/ncee The National Center for Education Evaluation and Regional Assistance
http://ies.ed.gov/ncser  The National Center for Special Education Research.

The Regional Education Labs http://ies.ed.gov/ncee/edLabs/regions offer a service that will review research on topics at your request.   A few results from my request for research on Value Added from my local lab, the REL Northeast and Islands, with their summaries of the research here:

• Getting Value out of Value-Added: Report of a Workshop. 2010; Braun, H., Chudowsky, N., Koenig, J.; The National Academies Press; 97 pages.  Source: General Internet search using Google Scholar  http://216.78.200.159/Documents/RandD/Other/Getting%20Value%20out%20of%20Value-Added.pdf  From the Background: “In 2005 the National Research Council (NRC) and the National Academy of Education decided to jointly plan a workshop to help identify areas of emerging consensus and areas of disagreement regarding appropriate uses of value-added methods, in an effort to provide research-based guidance to policy makers who are facing decisions about whether to proceed in this direction… A steering committee was formed to plan the event, facilitate the workshop discussions, and oversee the writing of the report. The committee members were chosen for their expertise in educational testing and accountability, valued-added methodology from both the economics and statistical traditions, and state and local data systems…This report is a summary of discussions at the workshop” (pp. vii-viii).
• Chapter 2, entitled Uses and Consequences of Value-Added Models, “provides an overview of how value-added models are currently being used for research, school and teacher improvement, program evaluation, and school and teacher accountability” (p. 15). This chapter concludes by stating that “[t]here was a great deal of concern expressed, however, about using these models alone for high-stakes decisions—such as whether a school is in need of improvement or whether a teacher deserves a bonus, tenure, or promotion—given the current state of knowledge about the accuracy of value-added estimates. Most participants acknowledged that they would be uncomfortable basing almost any high-stakes decision on a single measure or indicator, such as a status determination” (p. 25).

• Assumptions of Value-Added Models for Estimating School Effects. 2009; Reardon, S.F. and Raudenbush, S.W.; Education Finance and Policy; Volume 4, Number 4; pp. 492-519. http://openarchive.stanford.edu/susefaculty/reardon/assumptions-value%E2%80%90added-models  From the Abstract: “The ability of school (or teacher) value added models to provide unbiased estimates of school (or teacher) effects rests on a set of assumptions.  In this paper, we identify six assumptions that are required in order that the estimates of such models are well defined and that the models are able to recover the desired parameters from observable data.  These assumptions are 1) manipulability; 2) no interference between units; 3) interval scale metric; 4) homogeneity of effects; 5) strongly ignorable assignment; and 6) functional form.  We discuss the plausibility of these assumptions and the consequences of their violation.  In particular, because the consequences of violations of the last three assumptions have not been assessed in prior literature, we conduct a set of simulation analyses to investigate the extent to which plausible violations of them alter inferences from value added models. We find that modest violations of these assumptions degrade the quality of value added estimates, but that models that explicitly account for heterogeneity of school effects are less affected by violations of the other assumptions.”

• Evaluating Value-Added Models for Teaching Accountability. 2004; McCaffrey, D.F., Lockwood, J.R., Koretz, D., and Hamilton, L.; Santa Monica, CA: RAND Corporation; 191 pages.  http://www.cgp.upenn.edu/pdf/rand.pdf  As stated in the Preface, this monograph clarifies “the primary questions raised by the use of VAM [Value-Added Models] for measuring teacher effects, review the most important recent applications of VAM, and discuss a variety of the most important statistical and measurement issues that might affect the validity of VAM inferences. Although the document focuses on measures of teacher effectiveness, many of the points discussed here also apply to measures of school effects” (p. iii). The Summary explains several goals of this document: “to clarify some of the most important issues, to begin evaluating their practical impact, to spur additional work on these issues, and to help inform the debate among both researchers and policymakers about the potential of VAM. In the monograph, [the authors] clarify the primary questions raised by the use of VAM for measuring teacher effects, review the most important recent applications of VAM, and discuss a variety of important statistical and measurement issues that might affect the validity of VAM inferences” (p. xi).

• Would Accountability Based on Teacher Value-Added Be Smart Policy? An Examination of the Statistical Properties and Policy Alternatives. 2009; Harris, D; Education Finance and Policy; Volume 4, Number 4; pp. 319- 350; ERIC Document #EJ863334.  REL-NEI Webinar on Measuring Teacher Effectiveness http://www.mitpressjournals.org/doi/pdf/10.1162/edfp.2009.4.4.319  From the Abstract: “Annual student testing may make it possible to measure the contributions to student achievement made by individual teachers. But would these ‘teacher value added’ measures help to improve student achievement? [The author] consider[s] the statistical validity, purposes, and costs of teacher value-added policies. Many of the key assumptions of teacher value added are rejected by empirical evidence.  However, the assumption violations may not be severe, and value-added measures still seem to contain useful information. [The author] also compare[s] teacher value-added accountability with three main policy alternatives: teacher credentials, school value-added accountability, and formative uses of test data. [The author] argue[s] that using teacher value-added measures is likely to increase student achievement more efficiently than a teacher credentials-only strategy but may not be the most cost-effective policy overall” (p. 319). Also see The Policy Uses and “Policy Validity” of Value-Added and Other Teacher Quality Measures, by Harris (2007): http://www.wcer.wisc.edu/publications/highlights/v19n3.pdf

• Key Issue: Using Value-Added Models to Identify and Support Highly Effective Teachers. 2008; Goe L.; ETS; The National Comprehensive Center for Teacher Quality.  http://www2.tqsource.org/strategies/het/UsingValueAddedModels.pdf  When defining Value-Added Measures, the author states that “the value-added measure as it is used for evaluating teachers is calculated as follows: Students’ previous test scores are used to create predicted test scores for a given year. The difference between the predicted and actual test scores are growth scores. Teachers’ contribution to students’ learning is determined by looking at the average of all of their students’ growth scores. The teachers are then ranked against other teachers within a district (or other unit of interest) according to how much they contributed to students’ growth, and this ranking is their value-added score” (p. 2). The authors cautions that “though value-added models are useful in tracking student progress over time, there are limitations and complexities involving these methods and the resultant data, particularly when used as the sole measure of teacher effectiveness. Educators and policymakers should give careful consideration to these concerns before committing to using value-added methods in ways that may not be warranted, given the current state of our understanding about the methodology and theory. The bottom line is that value-added data are limited in what they can tell about teacher quality and effectiveness; these data are more useful when supplemented by other measures and sources of evidence” (p. 5).

• Models for Value-Added Modeling of Teacher Effects.  2004; McCaffrey, D.F., Lockwood, J.R., Koretz, D., Louis, T.A., and Hamilton, L.; Journal of Educational and Behavioral Statistics; Volume 29, Number 1; pp.67-101.  http://www.rand.org/pubs/reprints/2005/RAND_RP1165.pdf  From the abstract: “The use of complex value-added models that attempt to isolate the contributions of teachers or schools to student development is increasing. Several variations on these models are being applied in the research literature, and policy makers have expressed interest in using these models for evaluating teachers and schools. In this article, we present a general multivariate, longitudinal mixed-model that incorporates the complex grouping structures inherent to longitudinal student data linked to teachers. We summarize the principal existing modeling approaches, show how these approaches are special cases of the proposed model, and discuss possible extensions to model more complex data structures. We present simulation and analytical results that clarify the interplay between estimated teacher effects and repeated outcomes on students over time. We also explore the potential impact of model misspecifications, including missing student covariates and assumptions about the accumulation of teacher effects over time, on key inferences made from the models. We conclude that mixed models that account for student correlation over time are reasonably robust to such misspecifications when all the schools in the sample serve similar student populations. However, student characteristics are likely to confound estimated teacher effects when schools serve distinctly different populations. “

Visit the mail REL site http://ies.ed.gov/ncee/edlabs about  to find links to publications, work in progress, references, Ask a REL, and more.

http://cecr.ed.gov  Center for Educator Compensation Reform (CERC).  This isn’t exactly an assessment site, but using assessments to incentivize teacher performance for compensation purposes brings CERC into this arena. From the About Us section of the website: “The Center for Educator Compensation Reform (CECR) is the premier organization that works to raise national awareness of alternative and effective strategies for educator compensation reform. This website serves as the primary online repository for information, tools, and resources to support Teacher Incentive Fund (TIF) grantees, policymakers, state officials, and district professionals with the design and implementation of educator compensation reform programs and policies.”  The website includes state and district cases summaries, implementation guides, research syntheses, and a national map describing educator compensation initiatives across the country.”

http://www.ecs.org  Education Commission of the States (ECS)
From the About ECS Mission Statement: “The mission of The Education Commission of the States is to help states develop effective policy and practice for public education by providing data, research, analysis and leadership; and by facilitating collaboration, the exchange of ideas among the states and long-range strategic thinking.”
Included on this site is The Teacher Effectiveness and Evaluation Policy Issue section which provides a discussion of the policy issues related to defining and measuring teacher effectiveness, tools and resources that provide information about what other states are doing to address these issues, and a list of related research and websites. The direct link to this site can be found at http://www.ecs.org/html/issue.asp?issueid=129&subissueID=62.