Hey @Koroldev!
So what I would do if it were me, have a boolean in the gamemode that will be checked, say “Done school”.
Then in the LEVEL BP, on beginplay, you get gamemode, cast to your current gamemode, and GET “DoneSchool”.
Then if TRUE> Set the original set of NPC’s to Hidden in game → True and these OTHER NPC’s to Hidden in game → False!
TLDR; You make them all part of the level then toggle their interactivity/visibility based on a bool in the game mode! 