My experience is that one of the leading causes of the anglophone diaspora in Quebec are anglophone schools, even the ones that have good immersion programs, because often the message in that institution is that we are a minority and we are under attack. What kind of francophones are you going to meet in an English-speaking school when francophones are not allowed to go to that school by virtue of Bill 101, or the charter of the French language?
You're creating social segregation that could have consequences down the road. I would argue that the anglophone movement in Montreal that talks about partition of Quebec in the event of Quebec's independence is itself an extension of that mindset that finds its seeds in separate English schools.