From Threat Vector, by Tom Clancy and Mark Greaney:
He decided he would let off a little of the pressure Miss Melanie Kraft built up in him before heading back home to Chantilly to his bitchy wife and his checked-out teenagers.
While my initial thought was that to check out was being used to suggest that the teenagers had perhaps left home (vacated), I don't think that this really makes much sense in the above context.
So, what does checked-out teenagers mean?
It doesn't mean dead [as another user's answer, now deleted, suggests], except metaphorically. It means uninvolved, uninterested, tuned out, unresponsive.
Given the context of the rest of the sentence (clue: "bitchy wife"), I would interpret "checked-out teenagers" to mean that his kids are disengaged from any meaningful family interaction and he is using that general assessment of his family life to justify his current course of action.
Urban dictionary records usage of checked out as:
"someone who doesn't care about their job anymore and is about to quit."
The children are most likely a care-free, non-committal teenagers who are not to be relied on for anything much.
The children's presence or absence is of no consequence to the family and as such figuratively they have checked out of his life
