Differences observed in achievement levels for reading and math in Santa Ana's various ELD appeared to be due primarily to students' placement in a particular program, not relative effectiveness of the programs. That is, students were not randomly assigned to different programs. Students who entered Santa Ana schools above kindergarten level, and those moving between schools, were more likely to be placed in mainstream or mixed Transitional Bilingual Education or Immersion. And students in Immersion tended to enter (and exit) at higher levels of fluency.