
Wait behind
Remaining Behind
 Used when someone needs to stay while others leave, often for privacy or extra help. 
The teacher had Sarah wait behind to discuss her progress.
 Extra Attention
 Implies a need for individual attention, usually from a teacher or authority figure. 
James had to wait behind to receive feedback on his project.
 Delayed Departure
 Suggests someone is not ready to leave yet, possibly due to unfinished tasks. 
I'll wait behind to lock up the office.