This article is intended only for customers and partners using the Assessment Series.
CommonLit reports students’ scores on a scale that runs from 150-250, with higher scores indicating higher student performance. To create scaled scores, the difficulty of items and student ability are estimated using Item Response Theory (IRT) methods, and then these student ability estimates are translated to the range of scaled scores. This process ensures that students’ scores reflect their ability levels given the difficulty level of the assessment they took; it allows assessment scores from different assessments to be directly compared because each assessment has been mapped back to the same scale.
Scaled scores help teachers and administrators to identify which students may have struggled with the assessment(s) and which students performed well. These assessments also provide a way to measure students’ growth once they have taken two assessments in the series. The difference in students’ scores is discussed further in the article “How can scaled scores be compared across time?”