In the UK :  

youth A u16..6.93m - ~7m, ~same as us, 1 year offset younger kids
youth B u14..6.45m  - bigger than us
youth C u12..6.05m  - bigger than us
youth D u10..5.40m  - ~same
youth E u8..5.10m - do we have U8's?!

They're not falling apart, in fact, Le Poms seem to do pretty well ...

In the US (not so much a powerhouse anymore, but interesting all the same) :

17-18: Unrestricted
15-16: 6.78 meters (22'3")(48x15)
13-14: 6.36 meters (20'10.5")(48x16)
10-12: 6.00 meters (19’8”)(48x17)
For Juniors 16 and under who are competing in Championship team sprint, team pursuit, keirin, or Madison the 17-18 (unrestricted) gear limit applies.

I don't have the rules for other countries yet, watch this space ..