In elementary school, the correlation between IQ and grades and achievement scores is between .60 and .70. At more advanced educational levels, more students from the lower end of the IQ distribution drop out, which restricts the range of IQs and results in lower validity coefficients. In high school, college, and graduate school the validity coefficients are .50–.60, .40–.50, and .30–.40, respectively. The "g" loadings of IQ scores are high, but it is possible that some of the validity of IQ in predicting scholastic achievement is attributable to factors measured by IQ independent of "g". According to research by Robert L. Thorndike, 80 to 90 percent of the "predictable" variance in scholastic performance is due to "g", with the rest attributed to non-"g" factors measured by IQ and other tests.