Another perspective from languages with the same letters: From the time my DD was born, my DH (native spanish speaker) read to her in spanish and I in english. I speak english with her almost exclusively and I would say he is about 50/50 in what language he speaks with her. Based on some research I had read, I was prepared that her language would be delayed as her brain figured it out, but that wasn't our experience. When she began speaking, while she sometimes used a spanish word in an english sentence, it seemed clear that she was switching back and forth based on the situation and who she was talking to. She just turned 7, her spanish accent is indistinguishable from my DH. She is 3 grade levels ahead in reading english, and at grade level in spanish.
