But there is something depressing about the argument it uses. The BBC quotes Steve Sinnott, the union's general secretary, describing the plans as "pandering to the pushy middle classes".
As long as the left believes there is something illegitimate in parents wanting the best for their children, the Conservatives will have every hope of an eventual return to power.
Meanwhile Liberal Democrat policy still says that we shall improve state schools so much that parents will be happy to give up any say in which school their children attend. Oh yes, and this will be achieved without any noticeable increase in taxation.
I cannot see this policy lasting much longer, and something Norman Lamb wrote in the Guardian after he lost the Lib Dem Conference vote on the future of the Royal Mail should be read and understood more widely:
As a constituency MP I am forever having to deal with situations where those without power or influence are struggling to be heard by an unresponsive state provider. One of the biggest failures of the state has been the scandal of education provision, which penalises children from the poorest backgrounds. The growing educational apartheid in this country ought to shame us all ...
This should give Liberal Democrats a real opportunity to demonstrate our distinctiveness, willingness to confront difficult issues, and capacity for fresh thinking. As liberals we should be seeking ways of securing social justice using mechanisms that are likely be more effective than what the centralised state has been able to achieve. We ought to look at these challenges with a fresh perspective, finding new approaches to the delivery of core public services, emphasising localism and being open-minded about ownership.