Considering: Should I make my child respond to me in my language? and Enforcing minority languages at home
The child is currently 2 years 4 months old. I speak to her in foreign language X. Other people speak to her in native language Y.
Child understands X but prefers to speak Y. I think she finds Y easier to speak.
I want the child to learn to speak X. Until she starts speaking X she won't learn how to speak it.
So, from what age should I apply the tactic that "I will reply to you only when you speak in X with me"?