I wondered how I would get my future classroom to be so cohesive and collaborative. Lundy and Swartz wrote a great book on Creating Caring Classrooms (by the same name) that provides lots of practical examples for community building within the classroom. I also think restorative justice practices and the use of community circles to check in with your students and give everyone a voice are extremely important.
There was more going on in the Brazilian jiu-jitsu class than just a cohesive community. They were also all adults who wanted to be there and wanted to learn. Their investment was obvious. The students paid to be a part of the class they took time out of their day to attend class. As much as I'd like to say that every student who enters my class will be totally psyched to be there, I know that won't always be the case. It's important that teachers are explicit in sharing the importance of their lessons. You must tell your students why they are learning what they are learning to invest them in the learning process.
I think what stood out to me the most was the collaboration and sharing of knowledge between students. When I was a student myself I was often reluctant to share knowledge with my peers. I craved the "A" and wanted to have a better mark them them. I was missing the point. Sharing my knowledge and helping them have greater achievement didn't lesson mine but would have enhanced it.
Looking to the future I think it is important to allow students class time to share their learning with others. If they read a new chapter allow them 5 minutes to internalize and process or with a partner. Likely different insights would have stood or to each student and sharing these will enrich their learning.
Knowledge is meant to be shared not hoarded.