Well come to the big 3 boi. Also…

I say instead of kicking out the one who’s the lowest, one of them reveals themselves to be the traitor and either joins the League of Villains or is captured and with one seat unavailable, they choose Shinsou to fill in that space. To kick the lowest student out of the hero course would be akin to what happened with Gentle: purging the weak so the strong will emerge, which unless that student is evidently not up to code, is a major dick move.