The first successful intelligence test, the Binet-Simon exam, was used to identify children at risk of falling behind in school. Since then, IQ testing has made significant advances in technical assessment and scoring. Different school districts now use IQ tests differently: Some rely exclusively on IQ tests to place students in special education or gifted and talented programs, while others use the tests as one of many components for classifying students. Many psychologists and education professionals, meanwhile, criticize IQ tests as inaccurate or misleading.

Common IQ Tests

Testing children's intelligence can be difficult because they lack the attention span and accumulated knowledge of adults. Four common IQ tests are designed specifically for children, with different variants available for different age groups. Three versions of the Stanford-Binet test, one of the oldest IQ measures, and the Johnson-Woodcock Tests of Cognitive Ability are appropriate for children as young as 2. The Wechsler Intelligence Scale for Children measures children age 6 to 17, while the Kaufman Intelligence Battery for Children works for ages 3 to 18. Each test attempts to measure the same thing, but they vary in length, format and question type.

How IQ Scores Work

Different IQ tests ask different questions and, consequently, the same person might answer 30 questions correctly on a difficult exam and 120 questions correctly on an easier exam. Researchers compare performances on different tests to calculate the final IQ score. First, they calculate the average score and standard deviation, a measure of how spread out scores are, for a given test. They give the average score on each test a value of 100 and set the standard deviation equal to 15 points. Each point above 100 indicates higher than average intelligence, and each point below 100 indicates lower than average intelligence.

IQ Score Ranges

Roughly two-thirds of all scores, regardless of the exam, fall within one standard deviation of the mean. Since the mean is 100 and the standard deviation is 15, that means two-thirds of all children have IQ scores between 85 and 115. The term "high IQ" is subjective, but scores over 130, more than two standard deviations from the mean, are uncommon. Fewer than 5 percent of children score above 130, and fewer than 0.3 percent score higher than 145. Many school districts classify students with IQs above 120 or 130 as gifted, according to Duke University.

Testing Limitations

IQ tests are imperfect measures of intelligence. First, as Duke University notes, the tests do a poor job of differentiating exceptionally talented children, because the questions aren't precise enough to separate super-geniuses from ordinary geniuses. A more widely relevant criticism is that the tests tend to favor people from privileged backgrounds. According to SUNY-Suffolk, the tests are better measures of achievement than raw intelligence. Students who attend great schools and work hard in class have higher scores than children with equivalent native intelligence in less advantaged circumstances. Finally, "Psychology Today" notes the tests undervalue different forms of intelligence like creativity and morality.