This can be set by teachers when hosting a quiz. While choosing a mode - they can pick this one and host the game for all students in the class to play as a live game mode.
I dislike this feature that was added without an alert to teachers when I set up the game. It seems like it incentivizes students to be competitive rather than encouraging to each other, which is why I also turn off the ranking results on class assessments. As it is, my students were take a summative assessment on an essay they read for HW, and while they were scored on correct answers rather than total points, this feature seems like a petty way to introduce low-level bullying to the classroom in the name of “it’s just fun”. It was not fun for some kids with high anxiety.