Hi Jool,
Hmm. I'm a bit confused here.
Are you in the southern hemisphere? Your first post says "WA," which could mean Western Australia or Washington. The g'day implies Australia.
If you're in Australia, I'm afraid I have no advice regarding achievement testing; I barely understand how it works in the US/California.
Most kids offered a grade skip have already mastered a substantial amount of the material in the grade to be skipped. In particular, reading/spelling/vocabulary/maths are often already mastered through a combination of osmosis and extra work at home or in school.
Topics that might require extra work include history, geography, handwriting, grammar, etc.
You could always talk to the year 3 teachers. I did that when my son was offered a skip. You could ask for a meeting with them to go over what your daughter might need to work on.
During 2nd grade, my son's school gave him a pile of 3rd grade books to do in his spare time.
Sounds like Aussie has a reasonably open attitude toward grade skips?
Val