Some private grade schools cost as much, if not more, than in-state college tuition. I send my kids to public schools, but that's because I live in an area with decent public schools (by which I mean, schools full of kids who generally aren't disrupting the learning environment).
A lot of parents work in areas where decent public schools aren't nearly as available. In some cases, they are better off paying for private tuition than paying the absurd markup to live in the "good" school district. So I'm glad they made this tax change.