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]
(..) - They're breaking into his mind. It's like hacking a computer. All it takes is time. How much time? Depends on the mind. But eventually, it'll crack ... ... and his alpha patterns will change from this to this. When it does, he'll tell them anything they want to know. What do they want? (..)1999 The Matrix