Not integrating into the French-speaking community wasn't really a choice, and it wasn't just a reaction against anti-Semitism, which was also rampant among WASPs. McGill had quotas to prevent too many Jews from attending, for instance. What it came down to was culture and policies that kept French-Canadians an insular cultural group. It was a bit like other British colonial societies, like Singapore, where different ethno-cultural groups were kept separate by language and religion, with the English-speaking elite at the top of the ladder.
Even if a Jewish family wanted to send their kids to French school, they couldn't, because nearly all French schools were Catholic. Which is why Jews like Mordecai Richler and Leonard Cohen went to nominally Protestant schools (although Cohen went to a private Jewish high school). There were English Catholic schools but as far as I know, no French schools for non-Catholics.
Today, a significant part of the Jewish community is francophone because of immigration from France and Morocco. According to this analysis, in 2011 about 17% of Montreal Jews were francophone, but with immigration trends that is probably close to 30% now.
https://www.federationcja.org/en/jewish_montreal/demographics/