A review of the basic information on intelligence testing as a schooling practice is presented, including a discussion of what intelligence is and three psychological approaches to studying intelligence (psychometric, behavioristic, and developmental). All intelligence tests derived from the psychometric approach are standardized and norm-referenced. Some properties that tests do not have in common and which result in different types of intelligence tests include: (1) individually administered tests; (2) group-administered tests; (3) global versus specialized measures; and (4) measures of ability versus achievement. The distinction between aptitude and achievement is a source of controversy in the field of educational measurement that is far from being resolved. In terms of schooling practices, the inability to distinguish between the ability and achievement components of intelligence test performance is important to recognize. A "below average" score on an intelligence test may reflect a lack of opportunity for a child to learn what is required on the test, or it may reflect a slow rate of picking up information from the environment due to learning difficulties of the child. The former problem is one of achievement; the latter is one of ability. (RL)