Apologies if this question has been done before, I suspect however that most such threads regard the educational system as a whole.
Here is an initial argument in opposition of the question:
We presumably agree with the notion of equal opportunities for everyone. In particular, we expect children to be given equal opportunities regardless of their financial background since as children they can not influence this via merit / effort.
Now schooling is a very important factor for university and job opportunities. Further, education can be thought of as an positional good in that how 'useful' it is depends on how much you have relative to others. As a result, since private schooling (on average) provides better schooling in exchange for money, we can think of private schools as converting money into greater opportunities. Now since opportunities are limited, then accounting for the positional nature of education means that by sending your child to a private school you are actively harming someone else's child. Essentially the argument is that this is not fair to those children whose parents could not afford to send their child to a private school and that you are unfairly advantaged.
Since the action you are committing is unfairly causing harm to others, it is morally unacceptable to send your child to a private school.
So how would you respond to such an argument, and what do you guys think?