Had nothing to do whilst dd was having a guitaer lesson so looked at the lik to Casting Network web site, there is a section to contact them, so I did, with lots of questions.
To cut a long story short, they are American based by the looks of it and all the castings they offer are in America, one of the questions they answered about age said
"you will need to make sure to enter a work permit expiration date for your daughter, as it's a required field for all children under 18. It's important for casting professionals to know that she is legally able to work, should they want to book her."
We do not have work permits in this country and licences stop at 16 (at the moment).
It is exceptionally difficult for British children (or adults to that matter) to get permits to work in America and I would imagine that all their castings are that side of the pond too.
Basically, what I am saying is I'd forget Casting Website if I were you.

, free or not!