In case you weren't compelled by the moral issues involved in closing the achievement gap, there's a growing body of evidence to suggest that it makes some economic sense too. A recent report from McKinsey & Company has garnered a certain amount of headlines by proclaiming that the effects of the achievement gap are akin to a "permanent national recession."
The gist is that our GDP is $1.3 to $2.3 trillion lower than it would be if we closed the achievement gap. That's $3 - $5 billion a day (or about one Michael Bloomberg a week). Pretty stiff stuff.
The thing is, the report doesn't offer any clues as to how to solve the problems facing education, only saying that they should be solved. Well, duh. It's like going to the doctor with a headache, finding out you have a brain tumor, and then being asked to leave without being told what you can do about it. I guess it's good to know, but that's not necessarily helpful.
Maybe this is the symbolism that Eduwonk has been looking for. The image or idea that finally compels people to act. Maybe it will be that. More likely, it will be more fuel for every group to use to promote their own ideas for improving education (me included).