For a while, young kids should play a games-based judo approach. Fun preparations that build strength and coordination and familiarity with judo. But then at some point they have to move to "real judo." I'm not talking about adult judo - we start kids in regular adult classes at about age 13, depending on their physical size and maturity. I'm talking about an intermediate level between games-based judo and actual judo technique.
One indicator that they are ready to step it up a level from games to real judo, is that they understand and can abide by the gentleman's agreement at the heart of judo. I've mentioned this Judo gentleman's rule before.
The most central rule to judo practice is that if I am going to allow you to use my body to learn to throw hard and fast then you must save me at the end. You can throw with force, but you must support me and help me get into the proper landing position.
Without people abiding by this rule, judo falls apart and cannot be practiced. When kids are progressively demonstrating that they can take better and better care of their ukes, they can be taught progressively more vigorous judo.
Whit (age 9) is getting to this point and Knox (age 6) understands but can't get the skills together. I suspect these are typical ages for these skill development levels.
[photo courtesy of Stefan Schmitz]