Valerie Strauss makes a case against funding Catholic hospitals and schools. I think the argument is that
(1) it is impossible to separate the religious aspect of Catholic schools from the educational aspect, the state-approved non-religious textbooks have the flavor of both
(2) more importantly, non-Catholic schools have a weak union that accepts lower pay. By channeling funds to Catholic schools we will, in the long run, undermine the leverage teacher's unions have to extort higher wages and benefits
What I like about the analysis is that while it's not a traditional cost analysis it does successfully avoid any mention of the students. In general, when you're considering spending more money on schools, there are going to be (some) benefits for students. In the case of textbooks those benefits are small but if you acknowledge them you open the door to the idea that the other side has good points too.
To make a compelling case against the "corporatization" of education it's important to ignore how it is helping students. If your audience starts to think about poor Haitian kids going home unable to do homework because they can't afford $100 math textbooks it may feel terrible about sticking it to the kids. And as soon as people focus on the kids you've lost the argument.