We add to Duncan's statement: Making sense of tragedy requires a solid education
Arne Duncan was right to call attention to 9/11 as an important opportunity for teaching children about the heinous events of that day twelve years ago, about honoring those who perished, and about the value of "coming together" as Americans.
But he missed a terrific opportunity to remind American educators that kids need context and background knowledge if they're to make sense of 9/11—or, frankly, of much else, right down to and including what's going on in Syria today. That calls for a solid, content-centric K–12 curriculum, including lots and lots of history, geography, and civics, the great neglected subjects of the typical "social studies" curriculum. E.D. Hirsch's Core Knowledge sequence would be a swell place to start.
For the benefit of teachers (and high school/college students) who want to understand 9/11 in context, over the past dozen years we at Fordham have also produced three collections of terrific essays by thoughtful, eminent Americans on how to make sense of those events and what children need to know about them. You (and Secretary Duncan) can find this guidance here, here, and here.