This is a great forum that I have been reading for years and now I'd like to make a little contribution.
Bought my 9yr old a Giant xtc JR 24 Disc at the start of the year. Lots of people telling me go a bigger bike as it will last longer. I'm glad I went with the one that fit him best because he's able to control and physically handle / throw the thing around better.
His riding has come along way and that bike has fueled an addiction. Rides to school now and has built a little xc track in our front garden.
It has enabled us to ride Candlebark, Yarra trails, Lysterfield, Wombat and You Yangs as a family together. Heading to Forrest for the weekend.
Having the right bike for his size and ability meant that at first he was able to keep up with his mum and me and now he is beginning to surpass us. He leaves me behind on the climbs and did his first black run a few weeks ago at the You Yangs. Climbing up then going down.
The only mod I've made is to upgrade the pedals to Nukeproof Neutrons which he saved up for. (Should have seen the pedal rash!)
He's already pushing the limits but should be right for another year.
So from this parent point of view the right size now was one of the best decisions and family time investments that we made. His mates struggle on their larger bikes.
Hope that helps some of you who are looking for a bike for your kid. The Giant was the perfect one for us.
PS. We need new tyres soon. Finding it hard to find 24" decent tread and weight for a reasonable price. Any got any ideas? Found these on CRC. Anyone know if they are any good?
http://www.chainreactioncycles.com/au/en/schwalbe-black-jack-mtb-tyre-puncture-protect/rp-prod80072