The DAS provides a range of T scores from 20 to 80. However, this range is not possible for all subtests at all ages of the test. Table-18 shows the ages at which a child could, on each subtest, obtain the lowest T score possible (20) and the highest T score possible (80). For the lowest T score available (20), none of the 17 subtests provides this scores at the lowest ages. (Verbal Comprehension, normed for ages 2 years 6 months to 6 years 11 months, does provide a T score of 21 at age 2 years 6 months and 20 at age 2 years 9 months). At the upper end of scores, only 6 of the 17 subtests provide the highest T score. For example, although the Sequential and Quantitative Reasoning subtest provides norms from ages 5 years 0 months to 17 years 11 months, it is possible to obtain a full range of T scores (20 to 80) only between the ages of 8 years 0 months and 13 years 5 months. A five-year-old child who is administered this subtest and fails all items, obtaining a raw score of 0, would obtain a T score of 40. Conversely, a seventeen-year-old child administered this subtest and passing all items would obtain a T score of only 70.

The failure to have the same maximum and minimum T scores at the upper and lower limits (i.e., a T score of 80 or 20) throughout the test may affect how you interpret the profiles of children. On the core subtests of the Upper Preschool battery, typically administered to children aged 3 years 6 months to 5 years 11 months, two subtests (Verbal Comprehension and Early Number Concepts) have limited ceilings, resulting in maximum T scores of 71 and 75 respectively, while 3 subtests (Early Number Concepts, Copying, and Pattern Construction) have somewhat limited floor, with minimum T scores of 30, 31, and 30 respectively (see Table-19). On the core subtests of the School-Age Battery, typically administered to children between the ages of 6 years 0 months and 17 years 11 months, three subtests (Pattern Construction, Matrices, and Sequential & Quantitative Reasoning) have insufficient ceiling scores, resulting in maximum T scores of 75, 75, and 70 respectively, while 3 subtests (Word Definitions, Similarities, and Sequential & Quantitative Reasoning) have somewhat limited floor, with minimum T scores of 30, 30, and 32 respectively (see Table-20).

The range of DAS GCA is 44 to 175. This range is not available at some ages. For example, the highest possible GCA that adolescents who are aged 17 years 11 months can get is 156; the lowest possible GCA that children who are 2 years 6 month old can get is 53.

For children of very low ability, the DAS provides a procedure for calculation of downward extensions of the GCA. Table 5 (pp. 385-89) in the DAS Administration and Scoring Manual provides the norms for obtaining GCA scores as low as 25. In order to obtain extended GCA scores, the examiner administers the appropriate subtests for a particular level of the DAS (e.g., Upper Preschool). The examiner then converts the obtained ability scores to T scores using the usual subtest norm tables. However, the examiner uses the T score from an appropriate Reference Age Group for the level of the Cognitive Battery that was administered. The three Reference Age Groups available are 2 years 6 months to 2 years 8 months (Lower Preschool administration), 3 years 6 months to 3 years 8 months (Upper Preschool administration), and 6 years 0 months to 6 years 2 months (School-Age administration).

For example, a child of age 8 years 0 months is administered the Upper Preschool battery rather than the usual School-Age battery. The child obtains the ability scores shown in Figure 3. To calculate the T scores, the examiner uses the norm table for the Reference Age Group (3:6 - 3:8) (DAS Administration and Scoring Manual, p. 286). Using the sum of these T scores, an Extended GCA of 35 is found in Table 5. GCA Equivalents of Sums of T Scores for the Reference Age Group (p. 386 - 7).

This procedure allow examiners to administer the Lower Preschool battery to children up to the age of 6 years 11months, and the Upper Preschool battery to children up to age 13 years 11 months and still calculate T scores and Extended GCA scores.