I teach in Japan and the writing system is based in Chinese characters and two other character sets different from the Roman alphabet. For that reason I can teach letters and phonics to kindergarten students and it doesn't affect their L1 reading pronounciation.
I had a couple email conversations with a woman in Canada (Quebec, if I remember correctly)and she told me they were not allowed to teach English phonics or reading until the third grade. There must be strong reasoning for that. However, that reasoning may not be well grounded and I don't know if that rule was system wide or just that school.
I searched this yesterday when I first saw the post. I didn't find anything astounding but I have access to some electronic journals and I'll check those later to see if I can find some research on it. I'm sure someone's done a study.
I assume I'll find studies saying with time those problems that might initially appear with some learners are an orginanizational problem that will iron itself out in time. Also, that woman was in Canada where they are working to support French competence first, but in France I'm sure the students are pretty competent in French
