Iranian fourth grade students’ reading literacy scores showed a declining trend across three PIRLS cycles: 457 in 2011, 428 in 2016, and 413 in 2021. This trend study applied multilevel modeling to compare student level (Students Like Reading, Students Confident in Reading) and school level (School Emphasis on Academic Success) predictors across the three cycles. Data were analyzed using student weights (TOTWGT) and teacher weights (TCHWGT) via the EdSurvey package, and restricted maximum likelihood estimation was used for two level random intercept models. Results showed that the predictive power of “students confident in reading” increased significantly from 2011 (B = 10.81, p < .001) to 2016 (B = 16.67, p < .001), then slightly decreased but remained strong in 2021 (B = 15.44, p < .001). In contrast, “Students Like Reading” showed a decreasing trend, dropping from B = 5.94 (p < .001) in 2011 to B = 4.18 (p < .05) in 2016, and became non significant in 2021 (B = 1.23, p > .05). “School Emphasis on Academic Success” had small but significant effects in all three cycles (B = 6.11 in 2011, 4.41 in 2016, and 7.05 in 2021; all p < .05). Between school variance remained high (ICC ≈ 0.38–0.40) across the decade, which was nearly double the PIRLS 2021 international average (0.21). It is recommended that educational policymakers implement interventions to enhance reading student confidence and pay attention to reducing between school inequities.