I found the same thing. In the bit of rural Canada where I grew up, it was pretty standard for french elementary students to go on to english high school (with 1-2 classes/year in french, usually french & history or geography). We can all still speak french (with weaker vocab if we don't practice) but we didn't have issues with math/science jargon or having enough practice in english. A handful of students went to french high school but generally because they intended to go to a french university.