All children? And forbidden by whom? And why? Why would anyone do that? And you know you are speaking for ALL families? I doubt that.
Yes. As a rule, their parents, there was order, Their parents wisely determined through thinking and discussing and by experience, that their children would have a chance to make it in the new country t- to succeed, actually, by learning the language.
Every child I knew and everyone now an adult who grew up in those times, say that their grandparents or parents spoke german or Italian or so but that they never learned the language. And none of them really expressed regret at least to me, in general. Nobody in society nor at school ever talked about it, it was a family rule.
In other words, it was back when parents actually paid attention to what the other parents were doing for the good of their children and families. They wanted their children to assimilate.