I should be embarrassed to admit this, but I'm not: I was brought up in a household that practiced English immersion. Why? Because my Mexican-born father had originally tried bilingualism and ended up with an oldest son -- me -- who came home in shock after his first day in kindergarten because he couldn't understand what the other kids (obviously English-speakers) were saying.
Since my father thought it was more important for his children to know the language of the country we were living in than to try and retain Spanish, he and my mother started speaking exclusively in English. Thus kids like me who couldn't even understand our own maternal grandmother when she asked us a question in English eventually shed almost every trace of Spanish and started speaking English exclusively.
And I don't consider this a bad thing.