We recently mixed up our Mix-It-Up Lunch, a twice-a-year, all-school, community-building event in which the entire school sits together in mixed-grade tables during lunch. We typically invite our 8th graders to lead their table in conversation and some kind of guided activity before we disperse for all-school recess (which, as you can imagine, often finds students dispersing back to their typical peer groups).
A few weeks ago, we gave each table a lunch tray full of random maker/builder materials: a piece of cardboard, some duct tape, some large marshmallows, some mini-marshmallows, tooth picks, newspaper, play-doh.... You get the picture. (We are not a school with a strong "maker" identity -- yet.)
We gave them one (faculty-approved) song to think together about a possible monument they'd like to make. We gave them another two songs to create their monument. The only rules: Everyone had to add something to the monument, and every monument had to have a name.
The process and products were hilarious and heartwarming. I can't think of a reason why exercises like this couldn't find room in our school life more regularly -- or why an extension might not find its way into afternoon classes, or spark the next project-based activity.