Thomas & Collier Research

Research and Evaluation

in Dual Language Education

Dr. Thomas is a professor emeritus of evaluation and research methodology and Dr. Collier is a professor emerita of bilingual/multicultural/ESL education, both from George Mason University. Together they bring clear research findings to countries around the world. After having analyzed over 7.5 million student records from all regions of the United States, their research findings are very generalizable to all regions and contexts of the U.S. In addition, according to researchers from Africa, Asia, Latin America, Europe, Canada, Australia, and New Zealand, the Thomas & Collier research studies have been replicated in other contexts and have been found to be very generalizable to many other countries for educational policy making.


In their collaborative work, Drs. Thomas and Collier have contributed new theoretical perspectives for the field of bilingual/multicultural education. They are well known for developing the Prism Model, a theory and guide to empirical research. This model makes predictions about program effectiveness, from a theoretical perspective.


Drs. Thomas and Collier have tested the Prism Model by collecting and analyzing program effectiveness data, and they have refined the model based on empirical findings. They have also developed unique theoretical perspectives on analyses of longitudinal student data, to demonstrate the importance of following English learners' achievement over long periods of time, with school policy implications.


By following individual student progress over 5-6 years at minimum (instead of the typical 1-2 years), they have shown that the typical short-term finding of "no significant difference across programs" has misled the field and policy makers; whereas, long-term findings yield extremely significant differences among school programs.


They have found with consistency in each of their research studies that only high quality bilingual schooling has the potential to close the academic achievement gap. By introducing degree of gap closure as the primary measure of program success, rather than pre-post score differences among groups, they have shown that English-only and transitional bilingual programs of short duration only close about half of the achievement gap, while high quality long-term bilingual programs close all of the gap after 5-6 years of schooling through two languages.


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