What should I do?  It is normal for children who are becoming bilingual to switch between languages and occasionally mix the two languages. This is known as code switching. This occurs naturally and depends on the audience and purpose of the communication. Code switching generally occurs when a child is trying to clarify a statement or resolve an ambiguity. It is also used to attract or retain the listener’s attention and to elaborate. Children sometimes mix two languages when attempting to communicate a word or an expression that is immediately accessible to him in one of the languages but not the other. Like monolingual children, bilingual children also play with their two languages by making words rhyme, inventing new words or using certain words in inappropriate contexts.

Code switching and language mixing are mostly temporary phenomena in the second language acquisition process. As children become more adept in their two languages, the perceived need or desire to combine them is greatly reduced.
Children understand that each language has its own vocabulary and syntax. They also understand that certain people with whom they come in contact do ot speak both of the languages that they speak. Consequently, they learn to use only one of their languages with them. Parents are encouraged to speak to their children in their native language and/or designated “family language,” so as to serve as an appropriate and correct language model.