Our children have grown up learning both family languages and they are now teenagers. We are happy they can speak both languages, but are horrified by how much they mix the languages when they speak to each other. When they speak to people who only speak one of the languages, they do manage to stick to the right one. My wife and I have always been very careful to speak our languages “cleanly” , not mixing in any words from the other language. Where did we go wrong and what can we do?
Thank you for your question. First of all you have not “gone wrong” at all, you’ve done a fantastic job at raising your children to speak both languages! Sorry to start my answer with another question, but it needs to be asked: Why do you want your children to change the way they speak? From what you write, I can feel your passion for your own languages (I have been known to be a bit of a pedant myself at times) and that you like the languages to be spoken “purely”. However, as children grow up, parents can not really steer their choice of language. Most bilinguals mix their languages when they communicate with other bilinguals. This is called code-switching and has its own strict rules.
When a bilingual person speaks to another bilingual with the same language skills, both languages are active in the brain, ready to be used. When it comes to a choice of a specific word or term, the one which is most accurate for the context will be used – sometimes it happens to be in the other language. Note that code-switching only occurs in discussions between bilinguals. Like you say, when your children speak to monolingual people they do not mix their languages – a testament to your and your wife’s excellent work at bringing them up to be bilingual. When your dear teenagers mix their languages, what they are demonstrating is a great skill of using their languages in the optimal way, and I would say that is something to be proud of!
All the best!