Over the past few decades, Dr. Wayne Thomas and Dr. Ginger Collier have conducted research that illustrates the "how" and "why" of dual language immersion. Click the following links to discover more about their research.
North Carolina Study: http://gled.ncdpi.wikispaces.net/DLI+Research
NC Study Results (PowerPoint slides): Download Thomas-and-collier-published-graphs-from-nc-study
ASCD Ed Leadership article: Download ASCD Ed Leadership DLI article Thomas Collier
Books: http://www.thomasandcollier.com/publications.html
Monographs: http://www.thomasandcollier.com/major-research-monographs.html
Report: The Astounding Effectiveness of Dual Language Programs for All: Download TWIAstounding_Effectiveness_Dual_Language_Ed
Interview with Thomas and Collier: