Parents are concerned that children who have trouble in school will 'fall through the cracks' in the school system. [=will not be given the help they need; will graduate without anyone noticing that they are unable to do the work]
The program is meant to help workers who may have 'slipped through the cracks' [=who may have not been included in other programs] because of their age.
You ought to 'get cracking' [='get going; get moving'] on that assignment. [=you should start working on that assignment right away]
(..) - Uh, let's, uh, let's-Let's get things Moving along a bit, um... Who's next? - All right, let me take a crack at this guy, See if I can get him to talk. - Now you seemed a little off today at the meeting. - No, no, no, (..)2009 TvShow: Heroes Title: Chapter One 'Orientation/Jump, Push, Fall' Season: 4 Episode 1