Experts agree, and anyone whose ever taught a second language knows, the best time for learning languages is when children are young. After all, that's when we all learned our first language. Simply put, the human brain is developmentally at its prime stage for learning language in the earliest years of life. Moreover, study after study shows that children who learn a language before the onset of adolescence are more likely to have native-like pronunciation. A number of experts say this proficiency is related to acquiring the language before a physiological change that occurs in the brain as a child enters puberty. And as with any subject, the more years a child can devote to learning another language, the more competent that child will become in that language!
The National Science Foundation