Interesting. Here are the possible mitigating factors the day DS took SAT:

-- could not find EITHER of his acceptable calculators. Solution: borrowed the identical calculator from our neighbor.
-- could not find EITHER his school or state IDs. Solution: he used his travel id. BTW, we handle always these things calmly, matter-of-factly, no frantic search or "WHY don't you have them" type drama.
-- test was in a nearby school he'd never been to. But, he did see a friend/classmate.
-- classmate was in his test room. Hmm, is there a competition factor? DS is not competitive, but the friend is.
-- the test was at least an hour and a half longer than the ACT due to the mandatory essay, but the essay came last.
They put about 20 kids to a room, so it's nice and small but you are totally aware of how many finish before you.

On the other hand, the first time he took the ACT in 6th grade, he was self-conscious about being the youngest kid there though he did see a friend, he was one of the few not writing the essay, and was taking it the same time as his HS junior brother, and he did very well.