An item discriminability study of the Iowa Tests of Basic Skills Language Skills tests identified test items that are robust discriminators, psychometrically capable of separating low scorers from higher scorers in the language tests battery. The analysis was conducted by calculating a point-biserial correlation for each item on the four language skills subtests in spelling, capitalization, punctuation, and usage and expression. Results show the spelling test to be the most robust in terms of having the highest average point-biserial correlation and the highest total percentage of items meeting the discriminability criterion. The other three subtests clustered together far below the spelling test. The findings are intended for the use of teachers and administrators using this and other standardized tests for the same skills objectives, and teachers and test developers interested in developing their own assessment instruments. (MSE)