Peter's mother insisted he did not know his addition and subtraction facts.  His second grade teacher was surprised to hear this. Peter had had been slow to learn to read and was a poor speller, but he had always done quite well in arithmetic.  Even on pop quizzes he usually got at least 80% of the problems right.

Alerted by his mother's concerns however, the teacher observed Peter during the next two weekly math tests.  She noticed that Peter attacked the tests in an unusual manner.  He answered questions out of order, starting in the middle and then jumping around until all of the problems were done. As usual, his scores were in the B to B-plus range.

Intrigued, the teacher took Peter aside and asked him why he did his tests this way.  Somewhat embarrassed, Peter admitted that he had not succeeded in memorizing addition and subtraction  facts like the other children in the class, but he had worked out a system or timed math quizzes.  "First I find the easiest problem", he explained.  "Like here, it's 7 + 1, which is easy to figure out: 8.  Then I know that 7 + 2 has to be one more than 8, so I look for 7 + 2 and write 9.  Then I look for 7 + 3 and write 10, and next I look for 7 + 4 and write 11, and I go on like that until the times runs out."

Peter had figured out that the subtraction facts also followed a sequence, so he used the same method for subtraction tests.  When quizzed orally on math facts, however, it was obvious he had not memorized any of them -- although he could add and subtract in his head well enough to produce correct answers if he was given a little time.

Peter was obviously a bright and resourceful lad. The fact that he was not retaining math facts, however, combined with his other academic difficulties, suggested to his teacher that he might have a learning disability.  Peter's mother agreed to an evaluation.  As it turned out, Peter did have visual perceptual deficits that made it hard for him to remember many kinds of information. Peter was unable to picture things in his mind, which made tasks involving rote memorization very difficult.  Imagining the spelling of irregular words was also beyond him.  Peter read slowly because he had to sound words out as he went along; because he did not carry images of words in his head, he did not easily recognize words that he had seen before.  Although he used his superior intelligence to compensate for these problems and was passing all his subjects, Casey's evaluation suggested that with special education support he could do much better than the B's and C's he was earning.

Taken from Smith, C.R., Learning Disabilities, The Interaction of Students and Their Environments, 2004.