The Center for Advanced Research on Language Acquisition (CARLA) at the University of Minnesota (www.carla.umn.edu) supports a number of coordinated programs on research, training, development, and dissemination of information related to second language teaching, learning, and assessment.
CARLA's Immersion Education and Research unit is led by Tara Fortune. Here are sveral of her works that may be of interest:
Fortune, T. W. (2012). What the research says about immersion. Chinese language learning in the early grades: A handbook for resources and best practices for Mandarin immersion, 9-13.
Available at: http://carla.umn.edu/immersion/documents/ImmersionResearch_Fortune.pdf
Tedick, D. J., Christian, D., & Fortune, T. W. (Eds.). (2011). Immersion education: Practices, policies, possibilities (Vol. 83). Multilingual Matters.