1. Say that he needs more maturity and rhythmic development. This may come with time. Perhaps he can begin lessons in a couple years.
The problem is not with his rhythm, it is with the pulse. Play some music, either on piano or Cd, and ask him to join in with you to feel the pulse. Clap along together to a Cd. Rhythm is subdivisions of a pulse, if you can find the pulse, you will find rhythm soon enough.
How would that come if he is not exposed to music? He is 8 years old and the building blocks are all there. He needs a teacher to help find the music and overcome the natural limitations he may have. Do you only take students that already have the basic skills? If so you probably are not the right teacher for him, he needs someone who enjoys a challenge.
It's perfectly possible that the skill may develop more easily than you think (one can always hope...). It may be that the poor kid has never been exposed to something with rhythm! Or at least not been encouraged -- or even allowed -- clap or dance or bang along with the beat.
I have known several ballet dancers in my time with perfectly horrible senses of rhythm when they began, but who developed very quickly once they got the initial feel.
Of course. Two things develop rhythm:1) training of motorics2) training of the vestibular systemIMHO, the problem of abstraction (counting) with this particular student does not prove that there is no rhythmic feeling present.