Ignoring for a moment the French part and focusing on the immersion part, the shortcoming of this kind of educational program is that there is little or no home help for the student in the language of instruction (as aptly demonstrated by the writer).

From the pupil's perspective, if you live in a predominantly Anglophone community and you spend the vast bulk of your existence speaking virtually exclusively in English both at home and in the hallways at school, and mom and dad cannot help you with the homework because they can't speak the language, why is anyone surprised that you're not successful?

Some family friends enrolled their son in Mandarin immersion with a notion that he could learn what they perceived as the most important second language, but they ultimately withdrew him because they could not provide the help he needed at home.

This is not to diminish the joys of learning a second language (or third, or more), but the process cannot stop at the classroom door.