There are 9 years old that are tall and other not...
The smallest frame I've built was a 14.5" CS-016 from Peter few years ago.
Not sure if he can still source them.
They are still in service after 5 years of hard rides and jumps.
Changing stem length with the years.
Now that my kids have outgrown them, it is time to find new frames.
The drawback are: QR axles and 26" wheels which mean I can't reuse them, while all other components are still fine.
A 27.5" would have been better, if it exists.