A.V.
Your mileage may vary. However, my friend and I both enrolled our children into different dual language programs and both girls are doing well. In my case, my child learns Spanish half the day and English the other half. It is immersion for the language the child is not yet fluent in. Not only has she done fine, she's learned much about other people and cultures. I think that even if she doesn't continue into MS, she has a good foundation and it is easier for her to learn Spanish now than in HS. She enjoys it. Her math skills and English reading are above grade level. We actually did not know this was available at our school until we enrolled her and they asked if we wanted to be in the lottery. Yes, please! She will be in 2nd grade and we have liked all of her teachers so far. In our school, there are teams and each team has an English and Spanish teacher and they trade after lunch. They also make sure children have instruction on new concepts in both languages so that if a child misses a concept in one, they can catch it in the other. It is probably harder on the teachers than it is on the children.
ETA: It is also offered in other schools in our district in Chinese, French and I believe Russian as well as Spanish, but those programs are harder to get into. Ours is only for our school. You can't opt in. I do agree with Eric (though I am highly suspicious of his extra links) that it is an outgrowth in some areas of bilingual education. It makes it easier for schools with a high ESOL population, but also benefits children who speak both/either language.
