Investigated with a sample of over 25,000 students in the second, fourth, sixth, and eighth grades was the use of the Myklebust Learning Quotient (LQ) as one basis for classifying learning disabilities. Investigated were the distribution properties of the LQ when computed on scores from the California Achievement Tests, the Comprehensive Tests of Basic Skills, and the California Test of Mental Maturity. Analysis showed that LQ distributions differed among grade levels, subject areas, and gender-by-ethnicity subgroups. The LQ distributions showed reasonable normality in many cases, but selected distributions deviated from normality. Results showed that the use of a single cutoff value, as has been recommended for selection or classification of students, is inappropriate. The results also provided normative data for the selection of variable cutoffs relative to student subgroups. (Author/IM)