ACS and CYM:
Same situation here last year, when Ghost was 11 and in 6th grade. The test was SAT. Also taken at our local college, but in January. I do not think January is a busy month for SAT, but I don't know about ACT.
So Gost walks in and in the hallway he spotted his friend from fencing, one year older. This I think has made him feel more at ease. Besides Ghost there were 2 or 3 7th graders testing in the same room. I also believe that it has made HS kids more tense to see such a little guy sitting next to them. Ghost reported that girls were especially amused. He was asked how old he was, followed by a question which book he used to study from - none was the reply, to the horror of the other kids. There was also a comment about kids like that scoring higher than most HS juniors. Ghost was actually enjoying this short lived fame:-) Nobody has asked him or us, for that matter, why is he writing this test. But if they were, I would have answered that it was for a talent search. People generally do not ask further thinking that this is something they should be aware of:-)
I am past the stage of hiding my child's ability - I have to be loud to help him and others like him.
This year January SAT was not offered at our local college, so we had to make a trip to the U of U. There they had a special, separate room for talent search participants. Much less amusing:-)