I highly recommend French immersion. One warning though, friends who did French immersion definitely had worse written grammar in English. This mattered in first year university when everything is submitted in English. Their spoken English was perfect but they had less experience writing essays and such in English. You can easily compensate for this by monitoring their English writing skills, and anyway my friends quickly caught up in university.

French immersion is a wonderful opportunity. There are good customer service jobs that require bilingualism (English/French) as do most jobs with the federal government. I spent a lot of time and money learning French as an adult, and your child has a great opportunity to learn while they are young and without an additional cost!

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My prayer to you
Is that you do all the things you set out to do
And live your life the way you love

Thurston Moore, Psychic Hearts

Thanks portia. I was/am concerned about the development of english reading/writing skill. I hope this can be managed at home as you said.