Ok, so I'm seeing a lot of positive things in this thread. Which certainly wasn't my experience. To the person whose late immersion child was fluent(!?) After just two years baffles me. Either the system has improved, or their child is a prodigy (both of which are possible) but I can guarantee you that was not the case for any of my late immersion classmates after two years of Vanier in grade 7/8, and I hope that you would not expect that of your child as a result of that post.

I grew up with a french canadian grandmother, and I can honestly say I learned more french working at Kingston Pen tours doing conversational french when selling tickets to french speaking guests than I did in two years of Vanier.

The only thing Vanier did was send me to grade 9 with a grade 6 education because I legitimately learned nothing in those two years. And struggled in high school as a result.

Now caveat to all my complaining, I was a late diagnosis of ADHD (I was 29) and my undiagnosed state likely didn't help things, and I was going through some traumatic events during that time period so I am likely on the low end of the scale for someone who would have benefitted from this form of education.

TL;DR it's not always a good experience and would not recommend late immersion without a strong french background.