Ukulele Book 1 is the study/teaching book for the ANZCA Music Examination for ukulele, established by South Australian music teacher and lifelong uke player Lesley Gentilin.
TES, UK-based worldwide teachers network Ukulele lesson resources (ages 7 - 11) - free, downloads
(Powerpoint) as well as other great uke teaching resources further down the page.
Australian-based Rainbow Music has a 'Ukulele
Wheel' for transposition and other uses, fretboard stickers, charts and songbooks which can be purchased for use in teaching.
Ukulele Go has two great tools: find ukulele chords that sound great together: and nothing but great
ukulele chord progressions. They're instant and a wonderful catalyst for songwriting, as well as a helping hand to find missing chord/s from other songs!
I welcome additions to this list if you know of other, quality, schools or adults teaching resources!