At the beginning of every group class I set what the students and I call the Jam alarm. This alarm is scheduled to go off 5 minutes before the end of class. My rule is that when the alarm goes off we drop whatever we are doing and jam. The children look forward to the jam because it is fun and has a looser structure than some of our lesson content. I also use this opportunity to give the students a chance to learn how to communicate through music (whether they are aware of it or not). Each class I will give them one limitation such as picking only one instrument, only percussive instruments (drums, buckets, tamborines etc.), only pitched instruments (piano, boomwhackers, xylophone etc) or a type of song structure. This makes them think more critically about how to create their voice. The different instrumentation also insures that each jam will have different characteristics. It is amazing how the Jams improve from week 1 to week 8, purely because the students are learning how to listen and how to contribute.
These skills are invaluable to any musician. Not only is jamming and improvising fun and kid friendly, but it also assists in learning how to speak the language of music. If you want your child to be a musician it helps to not only read the language, but to communicate with it as well.