>(If I were to really get inflammatory, I might mention that school is a classic principal-agent problem, and the proposal failed because it tried to trade the agents' convenience for the principals' health. But that's another, uglier debate.)

Or, at least (to phrase it in a slightly less negative way) to trade relatively incremental, diffuse, and somewhat abstract benefits for the students with specific and sometimes disruptive change for parents.

Furthermore, just about any change to an accepted status quo--even if it's arguably a mild net positive--is going to have a lot of vocal critics. Those who like the change will mostly not feel very strongly. Those who don't like it or have just learned to live with the status quo will often hate it.