I have no objection to the idea. Many parents don't have the time or perhaps the inclination to make breakfast for themselves or their children in the morning. So if the parents don't do it then the state must step in. After all that is partly what the state is for looking after those unable or unwilling to look after themselves or their children.
As for the "tax grab on parents who already finance state education" well that's just how taxation works or should work. You take from each according to their means and give to those according to their needs.