Critical period of language acquisition

Bringing children up in a bilingual home provides many benefits and learning opportunities, and can be a real gift to them. Not only do they learn the two languages they are exposed to, but they also assimilate an understanding of grammar and how sentences are made across different languages.

Further, early exposure to two languages is advantageous to toddlers and preschoolers when there is a critical period of language acquisition, making it easier for them to learn new languages at a later age within the formal setting of schools and college.

http://www.irishtimes.com/newspaper/health/2011/0301/1224291075281.html