I'm a teacher too. We both know that, except in serious cases of bad behavior or outright abuse, we do sometimes and intentionally pair our group up students with others we hope they'll work well with. And sometimes tha means dick head boys with nice girls. But I've also put all the dickheads together in one group and let the nice girls have their own nice, high-functioning group, just to give them some relief. Guess which group always outperforms the others?