Phrase or expression to describe intentional upward discrimination when the favorable situation comes along

Question

An employee would normally come 5 to 10 minutes before 8 AM to the office or the least at the stroke of 8 AM when he has the main boss coming in everyday (never late unless informed).

What do you call the tactic or behavior when, when this employee would come 15 to 30 minutes late or at times 1 to 2 hours late (without bothering to inform) just because in absence of the main boss, a make shift intermediary powerless (authority is given by no real power) senior is placed to overlook the day to day activities. (I would say the above as tactic because it would be habitual on part of this employee and other peers tend to catch on to the tardiness.)

This would place not just the employee in trouble but also the toothless senior (for his inaction) if ever the usually unconcerned top management has any probing done ever due to any unfortunate circumstances as part of other unconnected damage-control campaign that they usually have.

Answer 1

The expression that comes to my mind is:

"When the cat's away, the mice will play," is a term most people can relate to. When the manager is gone -- be it on vacation or just away from her desk -- some employees act like a teenager whose parents are out of town.

They sneak out early or come in late. They chitchat with co-workers more frequently, usually about nonwork-related things. They make personal phone calls, take extra-long lunches -- heck, maybe they'll even enjoy a cocktail with their meal.
_{What we do when the boss isn't looking}

See also definitions at TFD.