I think of we the people funding children's education, rather than 'the government' ... that's just a way of saying. (Though it might have consequences: I'm happy to pay tax to fund other people's children's education. Tax is, in this as well as other public goods, just the price of civilisation.)
Be that as it may. The 'vouchers' idea for schools has been around a while. Rhodes Boyson, one of Thatcher's acolytes, proposed it way back in 70's, early 80's. But in the end Keith Joseph didn't like it so it died mid-80s. (Milton Friedman was on board, specifically, too.) Thatcher was disappointed.
The point of it, back then, was as an instrument of marketisation - hence Friedman, Boyson, Thatcher. The only way of allocating scarce resources, they all thought, was to create a market in it. Buy it, sell it. (Blair and his crew thought that, more or less, too - hence, well, lots of what Tony and Mandy and co. got up to. They also did some good things, Sure Start for instance; only tangentially marketised.)
Personally I think there are better ways to structure educational provision than by buying and selling. Some goods are not good to offer for sale. (There's a decent book on this line by Michael Sandel, What Money Can't Buy: The Moral Limits of Markets; I recommend it.)
One of the reasons people liked the vouchers idea back in the 80s was that it could be used to save the great public schools - Eton, Harrow, Winchester etc. from the depredations of evil socialists who saw them as pernicious. As one of those evil people, I was against education vouchers back then and remain so.
But anyway, it would take as long to introduce a voucher scheme as to restructure as a national education system. What to do for SEN kids now, meanwhile?