Wayne Thomas and Virginia Collier, two professors from George Mason University in the USA, have done a great amount of research into Mother Tongue instructional support for learners of English (EAL students). Their research concluded that the greater amount of Mother Tongue instructional support for learners of English, combined with EAL instruction, the higher students are able to achieve academically in English in each succeeding academic year, in comparison to learners of English with no mother tongue instruction. The most powerful predictor of academic success in English is formal tuition in the students’ Mother Tongue.
Collier, V.P., & Thomas, W.P. (2007). Predicting second language academic success in English using the Prism Model. In J. Cummins & C. Davison (Eds.), International handbook of English language teaching, Part 1 (pp. 333-348). New York: Springer.
Ovando, C.J., Combs, M.C. & Collier, V.P. (2006). Bilingual and ESL classrooms: Teaching in multicultural contexts (4th ed.). New York: McGraw-Hill.
Other interesting articles on Mother Tongue
Pollock, David C. Third culture kids : the experience of growing up among worlds. Trade ed. Yarmouth, Me : Intercultural Press, , c1999.
Explores the experiences of third culture kids—TCKs—kids who live abroad during a large part of their childhood, and gives advice for dealing with this upbringing.
Baker, Colin, 1949-. A parents’ and teachers’ guide to bilingualism. 2nd ed. Clevedon, England ; : Multilingual Matters, c2000.
Read the article “Can we do more to make our schools truly international?” by the author Eithne Gallagher, who also wrote the book “Multilingual Matters”.