Groupme. Largest group messaging app used, by far. There is also a large number using Discord, but that is mostly the more nerdy/gamer kids. No one wants to use

Groupme. Largest group messaging app used, by far. There is also a large number using Discord, but that is mostly the more nerdy/gamer kids. No one wants to use facebook, but unfortunately most of the parents use facebook so they are forced to use it by association.