I haven't done any recent studies on that. It's more of a general principle related to vitality. As you can imagine, if child care from zero to four or five years—depending on when school starts—is in English, that undermines linguistic security, which is hard enough to maintain as it is, even when kids are fully educated in French.
An underfunded school system means that extracurricular activities sometimes take place in English, for example. That, too, undermines children's linguistic security, and may get parents thinking it's just easier to enrol their children in English schools. Perhaps their child throws tantrums because they don't want to go to school in French because they're embarrassed. That's a personal decision, a decision nobody can criticize. Going to day care in French can be complicated.