DHS Secretary Napolitano said Tuesday that in the coming months children 12-years-old and younger will not have to take off their shoes to board airplanes, and they will get patted-down less frequently.
DHS and TSA have not said exactly how they plan to implement these new procedures. And since kid's under 16 do not usually carry ID for domestic flights, presumably the only way a TSA officer will be able to tell a child's real age is by scanning the date-of-birth on a boarding pass and quickly calculating how old the kid really is. Hopefully, this will not backfire and actually slowdown boardings.
TSA's current official identification policy is that only people 18-years or older have to show a photo ID to get on a domestic flight.