It is very dificult to say why, how and when children should start acquiring a second language. After reading different information about this topic, I think that for children is better if they start learning a new langauge in the early stages of learning process. The earliest they start the easier it is going to be learn it. In the society we life nowadays it is neccesary to know more than just one language in order to be able to interact with different people. For that reason children should start learning it as earlier as the can to become good speakers. Languages are tougth to children using different programs (flex, fles & inmersion) and each of them are used depending on what you want to teach, in what way.
Parents sometimes think that learn a new language can interfere in the learning process of their mother tongue, but in my opinion learning a new language enrich the mother tongue of the children.
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Another article about this topic: http://www.iteachilearn.com/cummins/mother.htm
