What percentage of francophones learning English learn it successfully, and what percentage of anglophones learning French learn it successfully?
And please don't use Montreal as an example; it's such a trilingual city one is exposed to language from birth onwards. Outside Montreal though (and I've lived in many parts of Canada, namely Victoria, Sidney BC, Vancouver, Toronto, Waterloo, Ottawa, Montreal, la Malbaie, and Roberval, for various reasons, usually professional), and I can say that most anglophones who learn French can't use it, and most francophones who learn English can't use it. Ottawa might be another exception alongside Montreal, along with francophones or anglophones living as minorities (eg francophones in Toronto or Anglophones in Quebec city). But for the vast majority, taxpayer money is being wasted.
Why not try a more efficient system? Here would be my recommendation:
1. Have all Canadian students start to learn Esperanto (extremely easy language) as a second language at the age of eight.
2. At the age of ten, give them a test. Those who pass can choose a second foreign language of their choice; the rest continue with Esperanto (after all, if you can't learn an easy language, how will you ever learn a difficult one?).
3. Those who failed can take the test again at the age of eleven. If they pass, they get to choose a second foreign language of their choice, and those who fail continue with Esperanto (after all, if Esperanto is that difficult, how will that student ever learn English or French, which are MUCH more difficult?)
4. at the age of fourteen, students are free to choose whether or not to continue studying a second language or specialize in other subjects. Through such a policy, it would be guaranteed that even the dullest students would be fluently bilingual in either French or English, plus Esperanto. And the brighter students would know a third language too. This would be a great improvement compared to the current monolingualism dominating most of the country. This could also save money on translation costs for government and business, by ensuring that all in the country could speak at least one common second language, a situation we don't have today despite all the money being wasted.
By 10, it's already too late IMO. I don't see any point in making children learn esperanto as a starter language and I don't see any value in making them wait until they are 10 to learn a language they would find more useful. I started in French as soon as I started in elementary school. That made it easy. The older a child gets, the harder it is to learn languages.