Difference between Terra Nova and IQ testsBy Inderbir Kaur Sandhu, Ph.D
Q: I just received by son's 7th grade Terra Nova tests, his Total Score was 91 and the IQ component of this test was 122. How does the IQ test on the Terra Nova compare to other IQ tests, such as the Wechsler Intelligence Scale for Children (WISC)? I don't know how to interpret these scores. Any insight would be helpful. Thank you.
A: The major difference here is that the Terra Nova is an achievement test whereas IQ tests (such as the Wechsler's and the Stanford-Binet) are ability/aptitude tests. This does not warrant a one-to-one comparison.
In principle, achievement tests are more directly concerned with what is taught is schools, which is not the case with ability tests. Most achievement tests items resemble closely to the knowledge and skills taught at school. As for ability tests, the skills tested may not be school based with less reliance to specific knowledge (e.g., analogical thinking, although essential for success, is not something that is taught at school). This is why students who score lower on an achievement test than on an ability test may be regarded as underachieving. However, this is not true as there is no single test to measure potential in general and perhaps a combination of different tests may be better to determine the potential of a student.
Furthermore, on ability tests, there are clear cut tests of nonverbal skills which may not be as important or sometimes on-existent on achievement tests. Therefore, students who may have scored very high on nonverbal tests but much, lower on verbal and quantitative parts of an ability test may be perceptually oriented, but this may not be regarded highly in school as school-based subjects are mostly about symbols, that are numbers and letters. There is hardly any room for those who are perceptually oriented. Such a student may be seen as underachieving at school.
The Terra Nova tests compare students with others in their grades around the nation. Hence, the scores are listed in percentiles, as in your case. It also includes a component that acts like an IQ test. This component measures the students' ability to use information and apply it to new and different situations. It also gauges how a student analyzes and employs higher-level thinking skills. But, do bear in mind that this is a very rough measure of intelligence.
In reality, these tests are just snapshots of a student's performance. To get a better and more detailed picture, you should ask the teachers if your son's test scores are indicative of classroom performance. To get his IQ measured, you would need to see a qualified educational psychologist who would also be able to interpret the scores and perhaps explain areas of strength and weakness by looking at both the IQ and Terra Nova test scores.
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