My sponsor teacher last year was really into incorporating mindfulness into her classroom. Whether it was just playing peaceful music quietly in the background while the students did their work, or sitting on the carpet taking mindful breaths and listening to a chime before starting a new activity. Students seemed to really grasp the idea and I believe that even if they were just doing it to impress the teacher, it obviously was having an effect on their well-being. I think that mindfulness in a classroom is most helpful with anxiety or disruptive behaviour.
Letting the students have extra time to wind down from one activity and transitioning into another by sitting peacefully and focusing on their breaths, gives them that time to think about how they may need to recharge or how they may better themselves for the next activity.
Here is a link to a starter lesson on mindful listening. https://e7n7r7a7.stackpathcdn.com/wp/wp-content/uploads/2015/06/starter-lesson.pdf