I think overall bilingual educators are effective because they take the time to get to know their students' families. This helps create a classroom that is more home-like. I was going to scan the article "Celebrating Teachers: Teachers of Dual Language Learners Making a Difference" from the August/September issue of Reading Today magazine but cannot get it to work. It was on pages 2 - 4. It is by the IRA President Carrice Cummins.
If schools (in California) really wanted to improve Bilingual Education, they would stop using the California English Language Development Test (CELDT) as a measuring tool for progress. The test has been revised to make it a bit more challenging, but the scores give the impression that students are actually learning English, when in fact, scores on other measures, i.e. California Star Testing, indicate the opposite. Annual Yearly Progress (AYP) scores used to show how the achievement gap is doing between the "haves" and the "have nots" also show that most districts in the US are not lowering that gap. So what you have is a test, the CELDT, that gives a false reading and a score, AYP that indicates whatever it is we're doing is woefully inadequate.
Aside from test scores, what we lack is a consistency in finding the right people to teach these students. The quality of the teachers who teach English learners/Bilingual classes varies from excellent to "why is this person teaching this class?" I'm not sure that this is a problem that districts can overcome under the current policies.