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]
(..) But, Orson! Trust me. I know what I'm doing. Okay. Oh, no! What, you didn't just crack that veneer again, did you? I have to go. Go? Go where? And then it was like (..)2006 TvShow: Desperate Housewives Title: Listen to the Rain on the Roof Season: 3 Episode 1