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]
(..) - FRIDAY? Do you see? The beauty of it. The inevitability. You rise, only to fall. You, Avengers, you are my meteor, my swift and terrible sword and the earth will crack with the weight of your failure. Purge me from your computers, turn my own flesh against me. It means nothing. We gotta move. (..)2015 Avengers: Age of Ultron
(..) Get what you need. Good evening, boss. - It's gonna be blood on the floor. - I got no plans tomorrow night. I get first crack at the big guy. Iron Man's the one he's waiting for. That's true, he hates you the most. Ultron knows we're coming. Odds are we'll be riding into heavy fire. (..)2015 Avengers: Age of Ultron