Differential Ability Scales (DAS) is a “battery” or a series of tests given individually to children to assess their cognitive skills and achievements, depending on the normal stages of development as per age brackets. Generally, it includes 20 subtests categorized as cognitive, diagnostic, and achievement tests. The Differential Ability Scales is flexible enough to cater not only to “average” students but also to those who are exceptionally bright or those who are “less able.”
The creation and development of the Differential Ability Scales are attributed to Dr. Colin Elliot, who first developed the British Ability Scales (BAS) in 1979. The BAS underwent several editions, until the first edition of DAS was finally published in 1990, and a second edition was developed in 1997. The Differential Ability Scales has three levels, the first being the Lower Pre-school level taken by children ages 2 years, 6 months to 3 years, 5 months. The second level is the Upper Pre-school, given to those from 3 years, 6 months to 5 years, 11 months. The School-Age level, on the other hand, is catered to students from ages 6 to 17 years, 11 months old.
The cognitive category of subtests often tests a child’s verbal and nonverbal skills, such as in word definitions, verbal comprehension — wherein the child is supposed to follow the test administrator's instructions — and copying, in which the child draws a copy of a certain design. Many recalling exercises, such as recall of digits and objects, are placed under the diagnostic subtests. In the achievement subsets, the child is to perform spelling, reading, and computation exercises, the items of which are all arranged in increasing difficulty. The number of subtests included in a specific Differential Ability Scales test will often depend on the level; for example, only four cognitive and two diagnostic subtests are included in the Lower Pre-school DAS.
The Differential Ability Scales attempts to interpret test results in a holistic way. Basically, the cognitive category determines the intellectual capacity of the child, represented in the General Conceptual Ability (GAC) score. Strengths and weakness, meanwhile, are measured by the diagnostic subtests. Results from each subtest are also evaluated, along with the child’s behavior during the whole testing process. In this way, guardians and teachers can plan appropriate methods of intervention to develop the child’s intelligence and abilities.