One of the hot books on the book club circuit right now is called Educated, by Tara Westover. It’s a memoir. She was raised in an extremist Mormon home (so extreme they thought other Mormons were sinful) under similar circumstances as you described. She did eventually escape that life and was able to gain an education, but it was unbelievably difficult and if she hadn’t had some help and been able to get some scholarships, she might never have made it. She recalls being in a college class and not knowing what the holocaust was. She was treated as a smartass who was being disruptive because it never occurred to anyone that someone could get to age 18 and not know that.
Treating children as if they are possessions and not individual human beings is an outcropping of patriarchal values. There have already been cases where the state has intervened in order to provide lifesaving health care over the objections of the parents. Why not as relates to education?