I speak English to my girl, my husband speaks French to her, we have a mandarin teacher come to our place twice a week since Zoe is 1.5 yrs old. Zoe now is 5 years old, she speaks good English, so so with French. Just surprisingly, Zoe speaks Mandarin fluently. Logically, Zoe should speak better French as she hears and speaks French every day at home with her Daddy, however, Mandarin is just twice a week. We believe it's all because of Zoe's Mandarin teacher, Zoe likes her a lot, she makes Zoe feel interested in learning Mandarin, that's why Zoe often asked me how to say this in Mandarin, how to say that in Mandarin. So I do believe the interest is the best teacher.