For most bilinguals, there is language shift and change. Languages do not stay static and equal. In the teens, there is often movement towards a prestigious majority language. Having worked so long and so hard to produce bilingual children and gained a measure of success, parents may find it hard to accept that their child prefers one language rather than another. A child may refuse to speak one language in the home, preferring to operate in the higher status language used in the peer group. This is quite customary among language minorities.
Even younger children refuse to speak one language. Sometimes this is because they have a stronger language and are able to express themselves better in that language. If one language is relatively underdeveloped, then a child is just being pragmatic. For example, if a child has a lack of practice in one language, then they are using the currently more proficient language. Occasionally, the child is also signaling something about relationships. There are occasions when one language is associated with a much adored person (e.g. the mother), such that the child tends to stick to that language.
Even the most loving parents may become tearful when their child does not respond in one of the parents’ languages. The worst choice is to abandon one language. That does the child no short- or long-term favors at all. At its worst, it abandons the chance of bilingualism in the future. The best choice is for the parent to continue to use his or her preferred language, even if the child does not respond in that language. The child is still becoming bilingual, or at least very ready to be actively bilingual.
Sometimes, rejection is short-lived. Just as adolescents go through fads and fashions with clothes, eating habits, sleep so there are language fashions. Language change may be temporary, reflecting peer-group culture, a symbol of growing emotional and social independence from parents and family life, growing self-assertiveness and the need for a distinct, independent self-identity from the family.”