I just noticed this bit on that website link:
To receive the correct Schoolkids Bonus payment in January 2013, Centrelink customers must check and update their details by 31 December 2012 if:
•you are or your child is starting primary school or secondary school in 2013
•your child’s care arrangements or any other details have changed
•you are or your child is finishing secondary study in 2012.
You can update your details through Centrelink Online ServicesLink to external website.
If none of the above applies to you, but you or your children are in primary or secondary school and you are eligible for Schoolkids Bonus, it will be paid to you automatically without the need to contact Centrelink.
so it looks like you need to check/update your info. I found the link under the Family Assistance Tab (on the left hand side of the Clink home page once you log in.)