The PIRLS assessment is designed to provide a complete picture of the reading literacy achievement of the participating students in each country. This includes achievement by reading purpose and comprehension process as well as overall reading achievement. Consistent with the goal of a comprehensive view of reading comprehension, the entire PIRLS 2021 assessment, digital and paper versions, consists of 18 reading passages and accompanying questions (known as items), half assessing reading for literary experience and half assessing reading to acquire and use information. In accordance with the group adaptive design, one third of the passages are relatively difficult, one third of medium difficulty, and one third relatively easy. Countries administering digitalPIRLS also administer ePIRLS, which consists of five tasks that assess online informational reading.

In order to keep the assessment burden on any one student to a minimum, each student is presented with just two passages, one literary and one informational, according to a systematic booklet assembly and rotation procedure, as described in the next section. In digitalPIRLS countries, some students also are presented with ePIRLS material, either two ePIRLS tasks, or one digitalPIRLS informational passage followed by one ePIRLS task. The PIRLS administration consists of two 40-minute sessions, one for each passage or task, separated by a short break, and followed by a 30-minute session for the student questionnaire. Following data collection, student responses to the assessment passages are placed on the PIRLS reading achievement scales using item response theory methods that provide an overall picture of the assessment results for each country.2

PIRLS was designed from the outset to measure trends over time in student reading achievement. Accordingly, the PIRLS reading achievement scale provides a common metric on which countries can compare their fourth grade students’ progress in reading over time from assessment to assessment. The PIRLS achievement scale was established in 2001 so that 100 points on the scale corresponded to one standard deviation across all of the countries that participated in 2001, and the scale centerpoint of 500 corresponded to the international average across those countries. Using passages that were administered in both the 2001 and 2006 assessments as a basis for linking the two sets of assessment results, the PIRLS 2006 data also were placed on this scale so that countries could gauge changes in students’ reading achievement since 2001. Following a similar procedure, the PIRLS 2011 and PIRLS 2016 data also were placed on the PIRLS scale, as will be the data from PIRLS 2021. This will enable countries that have participated in PIRLS since its inception to have comparable achievement data from 2001, 2006, 2011, 2016, and 2021, and to plot changes in performance over this 20-year period. 

The PIRLS reading achievement scale is an overall measure of reading proficiency that includes both reading purposes and processes of comprehension. However, in addition to the overall scale, PIRLS also provides separate achievement scales on the same metric for purposes for reading and for processes of comprehension. More specifically, there are two scales for reading purposes:

  • Reading for literary experience; and
  • Reading to acquire and use information.

In addition to these, there also are two scales for processes of reading comprehension: 

  • Retrieval and straightforward inferencing; and
  • Interpreting, integrating, and evaluating.*

Countries participating in digitalPIRLS also administer ePIRLS; so, in addition to the usual PIRLS overall reading achievement results and results by reading purpose and comprehension process, in countries participating in digitalPIRLS, student achievement will also be reported for online informational reading. The ePIRLS online reading achievement scale was established in 2016 to enable countries to examine their students’ online reading performance relative to their performance on the PIRLS reading achievement scales.

Retrieval and straightforward inferencing combines items from the Focus on and Retrieve Explicitly Stated Information and Make Straightforward Inferences comprehension processes. Similarly, interpreting, integrating, and evaluating is based on items from the Interpret and Integrate Ideas and Information and Examine and Critique Content and Textual Elements processes.