I have a giant, almost not ending PBL – building a robot – and a side effect is students running off at the mouth. One student has been a particular problem and was toxic. He slowed work down and made students uncomfortable. Some was flat out racist, some sexist, and some a bit locker room in nature.
I was trying to let the students work it out, but it just got worse and we are hitting a hard deadline.
I finally pulled him, told him his conversation was toxic, and put him on a solo side project. Had some blowback, he complained, an administrator talked to me and it got very comfortable but I stuck to it. I also made it clear we could not be successful without his contribution.
I did see the main project make good progress so positively reinforced that and on task conversations.
The solo project wasn't making satisfactory progress, so Wednesday, day before Thanksgiving break, I declared it help "Student X", made him in charge of everyone including me and we knocked it out. He was positively reinforced- he got caught up, he got to be in charge and felt included in the group again.
Win, win all around.