When I was 11, my parents bought me a small two stroke bike with a three speed and a clutch. It was frustrating for about a day and a half, but by the time that I was 14, I was able to drive the truck, the MG and my brother's Datsun, but don't tell him that.
I have a 15 year old in the house, and it's time to teach some clutch skills. A small, four stroke bike seems like the best way to accomplish this. Estimated height is about 5'4", and I prefer things that say Honda on them.
Any suggestions?
Are Honda Groms in your price range?
In reply to Tom Suddard :
You know, I hadn't looked. For some reason, I thought they were semi automatic or CVT.
We have a mid-'80s Honda XR80 dirt bike. I think we paid $800 about 5 years ago for a fully operational bike. It's perfect for this purpose assuming there is dirt/grass to ride it on. I crashed it crossing a wet asphalt driveway.
In reply to pkingham (Forum Supporter) :
That's about what I'm thinking of. I need to take a closer look at a few. They seem to be plentiful in that price range.
XR80 or XR100 is still the golden standard. They're damn near all the same from about 1986 onward.
If you want the magic red button to handle the starting and don't mind it being blue, a small wheel ttr125 would be a great choice, but a big wheel model would be more fun for the adult caretakers. 
Either way, you really get to rent them for as long as you like for $0, with about a $1000 deposit if you take care of them.
The xr80 for the win. We built a 2 stroke 50cc bicycle build. It was frustrating as the two stroke was finicky. Not fun while trying to learn clutches
Not my build, but representative.
