It is a well-known fact that the ability to decode printed texts is critical to reading. It is intuitive that the better your students can decode text, the better their reading comprehension will be. However, until now, no one knew what was the critical decoding threshold below which students would not be able to improve their reading comprehension.
In two large studies, ETS® researchers examined the relationship between decoding and reading comprehension. The researchers were not only able to find the exact threshold below which reading comprehension broke down, but also revealed that students below the threshold in grades 5–9 experienced virtually no growth in their reading comprehension over the course of 3 years!
The details of the research can be found in this 50-page peer-reviewed Journal of Educational Psychology publication. Below is the summary of the findings and instructional implications.
A study with 11,000 students in Grades 5–10 found a reliable decoding threshold (235 in Capti Assess) below which there is no relation between decoding and reading comprehension, and above which there is a positive linear relation. This means that the better students were at decoding, the better their reading comprehension was, but only if they were above the threshold.
Another study with 33,000 students in Grades 5–9 found that the students below the threshold had significantly lower initial reading comprehension scores compared to their peers. The students above the threshold exhibited an acceleration in reading comprehension growth as they moved up in grade level. In contrast, the students below the threshold had virtually no annual growth in reading comprehension over the period of 3 years!
Remarkably, the threshold and a lack of growth in reading comprehension among the students below the threshold remained stable across the grade levels. Regardless of grade level, a decoding score below the threshold reliably predicted low reading comprehension. Finally, there was a significant number of students who were below the decoding threshold even in Grades 10.