Standardized achievement tests represent achievement at only one point in time, whereas school grades represent achievement over a longer period and thus may also be influenced by other constructs such as self-control and motivation ( Rost, 2009). The association between intelligence and scholastic achievement seems to be stronger when using standardized achievement tests compared to school grades ( Sternberg et al., 2001 Rost, 2009). Cross-sectional and longitudinal studies indicated strong correlations, around r = 0.40–0.81, between the two (e.g., Sternberg et al., 2001 Deary et al., 2007 Mackintosh, 2011). Since the beginning of intelligence assessment, the predictive validity of intelligence test scores for scholastic achievement has been well studied. The primary purpose of the first intelligence test ( Binet and Simon, 1905) was to predict scholastic achievement in order to determine the best school setting for a child.

However, this conclusion has to be considered as preliminary due to the small sample of children observed.

The results revealed the predictive validity of currently used intelligence tests for longitudinal scholastic achievement in German-speaking countries and support their use in psychological practice, in particular for predicting averaged school grades. The WISC-IV showed no significant association with longitudinal scholastic achievement when mathematics and language were analyzed separately.

Furthermore, the IDS and the RIAS predicted both mathematics and language, while the SON-R 6-40 predicted mathematics. All four tests significantly predicted averaged school grades. School grades were collected longitudinally after 3 years (averaged school grades, mathematics, and language) and were available for 54 children ( M age = 11.77 years). We analyzed the predictive validity of four widely used intelligence tests in German-speaking countries: The Intelligence and Development Scales (IDS), the Reynolds Intellectual Assessment Scales (RIAS), the Snijders-Oomen Nonverbal Intelligence Test (SON-R 6-40), and the Wechsler Intelligence Scale for Children (WISC-IV), which were individually administered to 103 children ( M age = 9.17 years) enrolled in regular school. However, little is known regarding the predictive validity of well-established intelligence tests for school grades. Intelligence is considered the strongest single predictor of scholastic achievement. Department of Psychology, University of Basel, Basel, Switzerland.Gygi, Priska Hagmann-von Arx *, Florine Schweizer and Alexander Grob

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