I don't come from a country where boarding schools are common at all. Even private schools are not that common.
But I am sorry money does help provide a better education. Smaller class sizes, access to better resources, involvement in a wider variety of activities and trips. These are things that unfortunately state schools are not able to often provide. Is it fair? No. But I don't know very many families who would say if they had the money to send their children to a better school, they wouldn't do so. Some families work two or three jobs to ensure their kids have access to the better schools then what is available to them otherwise. Education of kids is something that does and should take a high priority in life.
I agree that high quality education is something to strive for. I disagree that in all countries you need a lot of money to achieve that (in many countries you do - but not in all). What you do need in any case is knowledge on how the educational system works etc.
Nonetheless, 'richer' parents will in general be able to provide more opportunities for their children in school and/or outside of school and that 'cultural' baggage will make it easier for them to succeed in life.
If public (and 'semi-private' - no tuition!) schools offer the same (or even better) quality as (than) private schools, money does not buy a better education. I was happy to grow up in such a country. Besides a few international schools, primarily students who failed miserably in their schools (many times because of behavioral issues) might end up in a private school for failed students - if their parents have the money for it. Certainly not the best educational environment. So, as I said, it is a matter of perspective.
Do you have this vision of boarding schools where they send their kids off and they see them once or twice a year??? Anyone argue that Diana didnt have a huge influence on her sons and how they grew up? They went to boarding schooi before Eton. And yet I dont see anyone arguing her and Charles had no part in raising their kids in their formative years.
I would argue that they would have had a greater influence had they not send their children to boarding schools and had less relied on nannies. It's not about influence or no influence but about more or less influence. And I am sure William and Harry would be able to explain very well how their nannies and some people at boarding schools 'shaped' them.
Boarding schools make sense for some people. For kids whose family are often on road for work it makes sense. This is why its common with children whose parents are things like diplomats or business. If their parents are traveling around the world the options are limited.
Royals dont choose boarding schools as they dont want to raise their kids.
I never argued they did. It is a consequence of their choices; and sometimes it's the only reasonable alternative to ensure a good education (although I know quite a few children of diplomats and business people and in most cases their mother is home taking care of them and driving them to their (international) school and sports etc - no need for boarding school). I was arguing that this isn't the best way to raise and educate your children.
They choose boarding schools for
1. the education the kids receive
2. the practical reality of their parents constantly being on the road
I fully understand that in some cases there might be good reasons to choose a boarding school. As you correctly state, educational quality is just one of the reasons they might consider it. The practicality of things might be as much a deciding factor; which shows that the choice is at least as much made because of the parent and not necessarily because of the child (although I assume they will look for a school that they would think fits the child - unfortunately, prince Philip failed miserably at it).
The reality is the Cambridge kids will spend much of their teen years being raised by someone other then their parents. Simple fact they cant take their kids every where with them. So will it be a nanny or will it be boarding school.
At least boarding school they get the sense of being like the other students. They don't go home to a nanny and servants. They live in dorms and have the same life as the other kids around them.
The saying is 'it takes a village to raise a child'; so any child will be influenced by parents and others. I just hope the parents will remain the 'primary' ones; and it seems that William and Catherine want to make sure that's the case. So, we'll have to see how that plays out in later years.
The final argument of the children living in dorms with other students (although a very select group) and in that way living a life a bit more 'normal' makes some sense to me; although I don't see why that can't wait until university. So, princess Elisabeth going off to boarding schools for the final two years of secondary schools makes much more sense to me than sending children or young teenagers to boarding schools.