Experts around the world have concluded that it is easiest and most effective for people of any age (children-adults) to learn to read in their mother tongue. Respected organizations such as UNESCO and SIL promote literacy programs in minority languages (like Romani). Such programs have been successfully initiated even where the minority language was not previously written. The educational system begins in the minority language. Once students have mastered the basic skills involved in reading (and writing), instruction in the national language is gradually phased in. At the end of such programs, students are equipped to successfully transition into opportunities for higher education in national language schools.
We would be very interested in hearing from any of you who have used such an approach. For those who would like more information, http://www.sil.org/literacy/multi.htm provides and introduction and list of resources.