Exhibit 1.1 shows distributions of student achievement for the participants in PIRLS 2016, including the average scale score with its 95 percent confidence interval and the ranges in performance for the middle half of the students (25th to 75th percentiles) as well as the extremes (5th and 95th percentiles). The PIRLS achievement scale summarizes fourth grade students’ performance answering questions designed to measure their reading comprehension across two overarching purposes for reading—literary and informational purposes, as well as a range of comprehension processes. The results for countries participating in PIRLS as well as its less difficult version, PIRLS Literacy, are reported on the PIRLS reading achievement scale. Both the PIRLS and the PIRLS Literacy assessments included 12 passages (6 literary and 6 informational) with four passages in common. PIRLS included 175 items and PIRLS Literacy included 183.
The PIRLS reading achievement scale was established in PIRLS 2001, based on the achievement across all participating countries, treating each country equally. The scale has a typical range of achievement between 300 and 700. A centerpoint of 500 was set to correspond to the mean of overall achievement in 2001, with 100 points set to correspond to the standard deviation. Achievement data from each subsequent PIRLS assessment have been reported on this scale, so that increases or decreases in achievement may be monitored across assessments. PIRLS uses the scale centerpoint as a point of reference that remains constant from assessment to assessment.
The results show that a number of countries performed quite well in PIRLS 2016, with 34 countries having higher achievement than the centerpoint of 500. The results also reveal that although the differences from country to country were small, there was a substantial range in performance from the top-performing to the lower-performing countries.