AKA, everything you think you know about learning languages is wrong and why it has major consequences for students today.
In 1998 California passed Prop 227 based upon the belief that total immersion in English was the best way to educate English language learners. While this seems logical and we've all heard the anecdotes about kids being language sponges and just 'picking up the language.' Research has shown that it's not so simple and English only hasn't been the magic bullet either.
The main problem is that we treat English language learners differently than we treat people who are learning foreign languages. The reality is that English languages learners are foreign language learners and what goes for learners of French, Mandarin etc goes for learners of English too!
Don't get discouraged, we actually have a pretty good idea what works when it comes to teaching English language learners. And the California Dept of Education has published a whole book on what works for teaching ELL's. But this is one of those areas where ideology and let's be frank, racism trumps solid research and methodologies.
For those of you who don't want to wade through all the linked resources. Basically what we've found out is if kids are literate in their first language it helps them to be literate in their second language. So when people talk about how their kids just picked up the language, what they neglect to mention is that they've been reading books, and teaching their kids how to read in their first language. Those spongelike kids also tend to come from a higher SES than the typical ELL in a CA school. Also most people are talking about their abilities to speak the language, not read and write in the language.
The next thing people don't realize is that there's a different between language used for interpersonal communication and academic language. Kids will almost always pick up interpersonal communication first, because that's your job as a kid :) But we test them on academic language, which tends to take longer to learn, especially when it's not used in the child's home environment.
So how to educate these kids? Well, that's a good question. The reality is that there's no magic bullet. There's not a perfect method. Because what works for one kid may not work for another, because our brains are all a little different. We do know that kids and adult learners of languages need a variety of approaches. We also know that people need to practice what they've learned and we need to hear words in a variety of contexts in order to learn them. Also use of the first language can greatly help with the acquisition of the second language, when used in the right contexts.
Finally, when it comes to kids and language learning. We need to keep in mind that their brains are still developing. Bilingualism is a long game. In general, most kids start out behind their monolingual peers and may stay behind them until around the 5th grade (10-12 years of age) What i've read is that their brains hit a major growth spurt around that age and all of sudden they have the brain power to catch up and then exceed their monolingual peers. (I'll link that reference when i find it again, for those who are interested)
With all this in mind i am in favor of a dual immersion program for kids that come from a home environment that has very little exposure to English and where parents aren't very literate in their first languages. Excellent programs will teach the kids the skills they need to be literate in the heritage languages and give them the resources they need to transfer those skills to the English language. In addition, kids who are in a good dual immersion program can reap many positive emotional benefits from the program that can set them up for lifelong academic success!
Final note, i kept this entry really general and not specific because I didn't want to bore you. Instead my hope was to give you a good overall picture. Feel free to ask me for specific in the comments! I'll update and add things depending upon your questions as needed.