(1) A student may be determined to have a specific learning disability based on a severe discrepancy between the student's intellectual ability and achievement in one or more of the areas listed in ARM 10.16.3019.

(a) A severe discrepancy is defined as a 50 percent or higher probability of a two standard deviation discrepancy between general cognitive ability and achievement in one or more of the areas identified in ARM 10.16.3019 when adjusted for regression to the population mean.

(b) Error in test measurement requires judgment for students who score near two standard deviations below the population mean. When exercising this judgment, consideration of additional information, such as classroom performance relative to the student's performance on norm referenced tests, shall be used as the basis for determining the severe discrepancy.

(c) Alternatives to norm referenced tests, such as curriculum-based assessments, shall be utilized to determine severe discrepancy whenever cultural factors, test conditions, size of test item sampling for the student's age, or other factors render standardized assessment results invalid. When utilizing alternative assessment procedures, a determination must still be made that a discrepancy between ability and achievement exists at a level of severity similar in size to the discrepancy that would have otherwise been found in (1)(a).