I am wondering about the ending statement in your comment: > As usual, it is hard to correct for other factors; children who grow up bilingually usually belong

I am wondering about the ending statement in your comment: > As usual, it is hard to correct for other factors; children who grow up bilingually usually belong to privileged classes. I am pretty sure that is true in Switzerland, but in the USA kids like that frequently start out in the lower-middle class (first generation Americans).