Most 9 year old girls, now look about like I did at 12/13.......so they all look like "big 9s" to me! You can always tell, though, by how they walk.........watch her sometime, they still walk like little ones! My son was 9 this trip, and really looks 9.......but still that was so close to the age, and having a big 2 year old who EVERYONE thinks is 3, I thought I might be pushing it, so I brought both their birth certificates, just in case. No one ever asked for them, though..........I didn't take them to the parks, I told dh I would leave them in the in-room safe and IF we had a problem, I would retrieve them..........that never happened. I have a 9 year old in my second grade class (Sept. bdate and repeated) and she just told me she's getting braces next week! I did not know they did that so early..........she does look at least 11.