Kid's Piano Is Childish
Kid's piano is childish, meaning that it must be brought down to their level. Adjust the height of the bar to fit the age of the child. There's nothing childish about kids piano, as taught by almost all piano teachers. But the opposite should be true.
The conventional teacher's approach is to usher the child immediately into the complex world of musical notation, with no introduction. There is no transition from what the child imagines the piano to be, to the reality presented by the teacher. What does a child imagine playing the piano to be? Most children take their image from the music itself, usually bouncy and fun.
Kids Need Fun First, Then Rudiments
We, as adults, know that "bouncy and fun" takes a lot of work and skill to be done well. Kids have no idea how much work it will take to play something with "bounce and fun," according to the standards of a piano teacher. But it is a mistake to immediately inundate the child with the rudiments of the skills necessary.
Lower The Bar
Far better to find what the child can play easily that equates "bouncy fun" to them. It may not be fun for the teacher, but that is absolutely irrelevant. The worst mistake for the teacher is to assume that what the teacher feels is what the child feels. A child can only feel what they do at the moment, they have little conception of moments beyond the present one.
To put it in terms a child understands, CHOPSTICKS and HEART AND SOUL are fine masterworks to which they can have immediate access. You won't have the same success with the original version of the MOONLIGHT SONATA. Lower the bar to where the child lives, and raise it later, as they grow. Let the child set the height of the bar, and go from there.