Re: homecoming
In the US, there is usually one major (American) football game at the high schools that is designated as "homecoming." Often alumni come back for this game. There is usually a homecoming dance associated with it, and a homecoming king and queen, as well as the homecoming queen's court.
The short answer is: A major social event for high school students.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.