We often get asked this very question, Why not wait and teach them in middle or high school when they have a better grasp on English? The answer is in the stats...
Studies have shown -- and experience has supported -- that children who learn a language before the onset of adolescence are much more likely to have native-like pronunciation and more likely to have lifelong retention. A number of experts attribute this proficiency to physiological changes that occur in the maturing brain as a child enters puberty. Of course, as with any subject, the more years a child, or anyone for that matter, can devote to learning a language, the more competent he or she will become. Regardless, introducing children to alternative ways of expressing themselves and to different cultures generally broadens their outlook and gives them the opportunity to communicate with many more people.
"While new language learning is easiest by age 7, the ability markedly declines after puberty. "We're seeing the brain as more plastic and ready to create new circuits before than after puberty," according to Dr. Patricia Kuhl. As an adult, "It's a totally different process. You won't learn it in the same way. You won't become (as good as) a native speaker."
Additionally --and In most cases -- learning another language enhances a child's English ability. Children can learn much about English by learning the structure of other languages. Common vocabulary also helps children learn the meaning of new words in English. Studies continue to support that no long-term delay in native English language development occurs between children participating in second language classes and those schooled exclusively in English. On the contrary, children taking second language classes score statistically higher on standardized tests conducted in English. A number of reports have demonstrated that children who have learned a second language earn higher SAT scores, particularly on the verbal section of the test. One study showed that by the fifth year of an immersion program, students outperform all comparison groups and remain high academic achievers throughout their schooling.