Most parents won't react to this by choosing to home-school. Presumably @TheSillyGoose had previously considered home schooling (as many families do) but had decided on balance that although she liked the idea, private school was a better option.
And then VAT changed the balance (by increasing the overall cost of private education, and reducing her goodwill towards the state) and now she's made a different choice. Because that's what she thinks is best for her family now.
Unfortunately as @twistyizzy says, the negative consequences of her new choice for the UK are high. But whilst I'm sure @TheSillyGoose has considered that - doctors generally have a strong sense of responsibility - her choice needs to be made for her family. And see above about reduced goodwill.
That's what some people don't seem to understand. Everyone has their own aims and preferences and they weigh up their options against their own preferences all the time. Seemingly small external changes can tip that balance and change behaviour - making a better choice (from their current options) for that family, but a worse outcome for the UK.