You're urging VAT on private education that you've used, because you're saying it's an unfair advantage, but now you say it wasn't an advantage at all for your children?
Did you, or didn't you, pay VAT on that private school? Because if you didn't (and I know you didn't, because no country taxes education) then perhaps you should. Was the "other country" the UK? In which case please use the link I just shared and pay up. If you won't, then why not....why would you demand others pay taxes that you've been "lucky" enough to be exempt from?
Then you said "state school parents are more supportive of the system because of grammar schools. Do NI Grammar schools have more resources? You've said they have more private donations (VAT-free) - and you've said that's both a good thing and a bad thing?
Now you've said "the taxpayer contributes" to independent school. Er....kind of the point....the taxpayer doesn't pay.
Your story sounds, at best, a muddle.