I believe one of the commentators (Marc, I think) is right when he says the parents should speak with the kid in their own language and be strict about it. My sister has lived in Germany for over 20 years and has two kids. With the first, Isabela, she would only speak in Portuguese. Nowadays, Isa speaks very good Portuguese, although with funny accent (like the kids in the German immigrants’ area not far from where I live). But with Luca, my sister was not strict, and then there was already Isabela in the conversation. As a result, he can only understand basic Portuguese and mumble two or three words. A pitty.

Saludos desde Garibaldi, in the heart of Brazil’s most important região produtora de vinhos =)