I don’t really get the orgy/group part of the game I’ve pretty much done everything there is but still didn’t unlock source of hints towards how to get those scenes.
You need to have both girls at max affection and max desire. You also need to have talked "about other girls" with them in the school breaks. After that, the threesome option will show up when you call them to the lockers.
This will already be made more clear in the next version.
