Hi I would check the top tube length on a 14″ scandal before building one into a kids bike. The on one frames come up quite long.
I looked at one when I built my lad his new bike but ruled it out for this reason and bought a 14″ kona frame as it was still fairly light.
Scandal
C Effective Top Tube Horizontal (mm) 562
http://www.on-one.co.uk/i/q/FROO26SCVD/on-one-scandal-26er-vertical-dropout-frame
Here is the geo for an Isla bike Bienn 26 large aimed at kids 11+
Top tube effective length: 538mm
Seat tube length: 410mm
Head tube angle: 70 degrees
Seat tube angle: 74.5 degrees
Bottom bracket drop: 40mm
Chainstay length: 430mm
Head tube length: 120mm
Fork length: 390mm
Fork rake: 40mm
Wheelbase: 1044mm
Stack: 527mm
Reach: 400mm