I think it's all a gimmick too. I don't know how many free school meals the VAT would "buy". When the coalition abolished the "Sport in Schools" initiative, it promised to give the money back to schools. This money was a few pounds per school and schools could have just about bought a single new football for the whole school.
The average annual fees for day pupils is about £16,000 and 80% of parents of children in independent schools have an income of over £50,000pa - so the issue of choice is quite clearly nonsense, because the vast majority of households do not have a spare £16,000pa per child. Increasingly, schools are relying on overseas pupils, which is why I wondered if overseas parents would be exempt.
I would be in favour of abolishing charitable status, but not to fund free school meals for all pupils. The FSM eligibility criteria urgently need reviewing, especially as Universal Credit rolls out, because there's a cliff edge. It's almost impossible now for the children of parents in work to be eligible for FSM, which is a major disincentive for people to come off JSA and take low paid work. However, I think there are better ways that schools could use any extra cash.