Some families choose to send their kids to Independent schools so that they develop religious tolerance through understanding.
Many government schools lack any kind of information sharing on any faith... so the kids grow up suspicious of religion. Whether any faith is "right" or "wrong" is beside the point. The reality is that we live in a world where the majority have faith in some form of God/superior entity and increasing tolerance through understanding is going to bring us closer to being able to live peacefully with each other... not trying to pretend it doesn't exist.
Also apparently going to school in a clean, attractive and respected environment helps kids to learn because this positive environment reinforces that they are valued. Putting kids in run-down classrooms with broken facilities is a non-verbal way of saying "You are not important enough". This makes kids resentful... and many start to believe what their environment is telling them.
Also, I see lots of parallels between private/public healthcare and private/public education. Everyone deserves the best of both these services... and no one should ever have to choose an inferior service for a "principle". So many people try to convince me that I don't deserve the best education and should go to public school out of principle. To me this is like saying "Oh no, I won't use that private hospital... I'll just wait on this 3 year waiting list and make do in the public hospital system because it's unfair to everyone else... even though if I make enough financial sacrifices i could afford to be treated tomorrow in a good, well run, clean private hospital. The martyr philosophy just isn't logical.
I believe if everyone paid a bit more than the public "voluntary" fee for public education they would see a massive improvement. I know for a fact that the voluntary school fee at my brother's school is only $50 a year... and that only 28% of families pay it! THAT demonstrates how much the average family values a good education. Even people on social security payments spend more than $50 a year on entertainment... hmmmm.