In international large-scale assessments, students may not be compelled to answer every test item: a student can decide to skip a seemingly difficult item or may drop out before the end of the test is reached. The way these missing responses are treated will affect the estimation of the item difficulty and student ability, and ultimately affect…

The Progress in International Reading Literacy Study (PIRLS) has been monitoring international trends in reading achievement among fourth-grade students for 25 years. As a critical point in a student's education, the fourth year of schooling establishes the foundations of literacy, with reading becoming increasingly central to learning across all…