•The maintenance method is typically employed with students who understand no English at all. A bilingual teacher teaches them fundamental math and reading skills, for example, in their native language first then begins teaching the same curriculum in English, using the native language to fall back on. The method aims to foster parallel learning development in both languages.
•With the transitional method, bilingual instructors teach classes in both languages, principally in the native language at first and then increasingly in English as students’ proficiency in it increases.
•Both methods (maintenance & transitional)  are designed to teach students of all abilities, from beginners to advanced English speakers, but individual districts select which approach best suits its goals. To start maintenance or transitional programs, schools must enroll a minimum number of limited-English-speakers.
Please add comments with your experience with those methods.