This is the 515th most frequent German word.
wann
"Whenever" or "at what time" (depending on context).
'Wann' is used here as a question word to inquire about the time an event, the start of the movie, will occur.
Wann beginnt der Film?
When does the movie start?
'Wann' is used here in an indirect question within a statement to refer to the time of his arrival without directly asking.
Ich weiß nicht, wann er ankommt.
I don't know when he arrives.
'Wann' is used here in a reported question that expresses a query about the time the school ends, integrated into narration.