I don't have any experience with the SAT10, but my DS8 has a similar reaction to speed requirements. He gets so panicky that his brain pretty much shuts down. It's almost phobic. He had time to spare on the timed math section of the ITBS, so it wasn't a problem at all.

However, the time might become a bigger factor as they get older. I can't speak to that either since we only did early elementary level testing so far.

Kriston