It's a commonly held belief among American language educators that the only way to teach a child (or an adult, for that matter) a second language is to fully immerse he or she in the language's vocabulary and lexicon. Structured immersion, as it's widely known, is a system of instruction by which the teachers speak to the language learners in nothing but the language they are studying, even if the instructor's words and sentence constructions are on a level far above that of the student's understanding. Sit in on any high school Spanish class, and you'll see this method at work.

Structured immersion does, of course, have its benefits. Fully immersion students in a language allows them the opportunity to truly adapt to the phonetics of the words themselves and understand, on a basic level, how phrases are put together. And certainly any intensive study of a language will achieve some results (though it's unclear whether or not students will retain the information after the class has ended). But structured immersion becomes problematic by way of assumption; assuming that students will naturally pick up a language by hearing it constantly is a logical fallacy. This is, after all, second language acquisition, not first. The rules are a little different.

To simplify a very complicated theory, first language acquisition (what happens when a child is first exposed to language) is believed to be tied to the properties of vocabulary naming. Children learn the word chair, for instance, because that is the only option they've been given for the object. A child's first basic lexicon is built of the words they've heard used for the things surrounding them. But when more than one word is presented for an item (such as mom or mommy, dad or daddy), the child will often latch onto to only one term. At times, he or she will shift back and forth between the terms based on context, but there will usually be a clear preference.

Second language acquisition, on the other hand, is based on providing substitutes for an already learnt lexicon. Even if the language learner is a mere five years old, he or she has already latched onto the most comfortable terminology, thereby creating for him or herself a first language. Anything thereafter will be an alternative and significantly more difficult to understand.

There is no conclusive research that an environment devoid of that first language will provide any student with a more rounded learning experience; if anything, it has the potential to confuse and frustrate students already so connected to their first language by shunning that linguistic backbone and refusing to acknowledge the lexicon they've known for so long.

Structured immersion is by no means an irresponsible, or even incorrect, way to teach a second language. It's benefits are clearly outlined for any educator who wishes to instruct in such a manner. But in order to truly reap those benefits, one must understand that structural immersion does not erase the linguistic rules of second language acquisition. There is no magic way to learn a language as if it were your first.