Ultramarina - the hyperactive/impulsive ADHD kids are likely to stick out like a sore thumb even 1:1, even if they are still pretty well self-contained/behaved for THEM the tester is STILL likely to see enough to imagine what that kid must be like outside. But the primarily inattentive kids, I would add especially girls, are much harder to pick in a room without distractions, engaged by a person they have good rapport with doing something they find at least moderately engaging.
I don't know about your kids but my kids find IQ tests pretty fun, especially with an engaging tester. My more gifted child even more so, she has come out positively glowing from both her IQ tests.
Some kids with ADHD have patterns in their subtests that show it, not all do. Some kids it really does come down to history taking and observation in situ. I heard an expert talk on ADHD last year who talked about making a mistake early in his career with a girl who tested and interacted beautifully in his rooms, so he declared her to be perfectly fine despite parental concern. The parents/school begged him to come see her at school (a new idea for him back then). He went, and as he was walking down the hall talking to the principle they heard a commotion. When they got to the girl's class she was standing on her desk dancing and flinging her clothes around. This was quite a lightbulb moment for him in terms of believing the history of the parents and teachers that see the kid every day.... I am guessing your daughter is not dancing on tabletops in the classroom, but you get the idea. For some kids it won't be obvious under ideal circumstances, particularly if they are gifted and/or a girl and are purely inattentive not hyperactive or impulsive.
