I must admit that I am at a bit of a loss here. This is like trying to reason with a toddler, and unfortunately I am not particularly good at trying to argue with those for whom rational thinking is not a learned skill.
The state provides access to free primary and secondary education for each and every child in the UK. There is no need for parents to send their children to fee paying schools, therefore fee paying schools are not essential.
That some people can afford it, and choose to do so is a private matter and is entirely up to them. They are, quite rightly, free to go down that avenue. But their choice is, like most other services the public chooses to consume, vatable.
The above is not a claim. The above is fact. You may not like it but that does not give my point any less validity.