"upon leaving school"
he was called up for the draft upon leaving school.

Hi~
I want to know the meaning and usage of "upon" here in this sentence.
Does it mean " toward leaving school" or maybe "directly after leaving school"?
Thanks a lot!

Question

"upon leaving school"
he was called up for the draft upon leaving school.

Hi~
I want to know the meaning and usage of "upon" here in this sentence.
Does it mean " toward leaving school" or  maybe "directly after leaving school"? 
Thanks a lot!

Answer

"Directly after leaving."

An example: "Upon leaving school, he immediately went to a bar and started drinking."

Answer

upon leaving = right at the point of leaving
He barely had one foot out of the door and he had to join the army. Sucks, huh?

Answer

it says simple future continous tense there.
upon leaving after leaving