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]
(..) Here I am. Costing the tax payers money... and... Sweating in my armchair. Y'know. I've been here for years and I still can't figure out how the system works. I've got a crack dealer who's doing months... And then I have a lady who accidentally backed into a mailman... Who's doing years. (..)2013 TvShow: Orange Is the New Black Title: I Wasn't Ready Season: 1 Episode 1