My son was like that last year. And badly so: the one time I saw what I felt was a truly worrisome ASD trait was when we tried to help him drill his arithmetic tables with xtramath.org -- he went deer-in-the-headlights when the smiley faced timer was on, and when I hid it and he couldn't remember a number instantaneously he would start banging hard on his head with his fists frown.

This year (2nd grade) his teacher has 4 rules for the classroom, the last one of which (right after "give me your best work") is "mistakes are expected -- if you didn't make any you wouldn't be in school". It seems to have helped quite a bit (he quotes the rule to himself -- and to his father -- at home).