Received: June 30, 2022 Revised: July 23, 2022 Accepted: July 23, 2022 † Correspondence: Jisun Choi, jschoitou@gmail.com ORCID: https://orcid.org/0000-0002-6270-4076 JERM 2022;32(3):373-394. eISSN 2288-8357 https://doi.org/10.29275/jerm.2022.32.3.373 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/4.0), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright © The Korea Society of Educational Studies in Mathematics JERM Journal of Educational Research in Mathematics Original Article Relating Students’ Early Algebraic Thinking to Mathematics Curriculum Materials Gwisoo Na 1 , Jisun Choi 2† 1 Professor, Cheongju National University of Education, 2 Assistant Professor, Gwangju National University of Education, South Korea Abstract This study investigated the trends in algebraic thinking of Korean elementary school students through the students’ correct answer rates for the early algebra-related items in the 4th-grade assessment of TIMSS 2011, TIMSS 2015, and TIMSS 2019, and explored these trends in relation to the changes in early algebra-related content in the Korean mathematics curriculum and textbooks. As a result of the study, with regards to finding unknowns or unknown operations and representing problem situations as expressions, the correct answer rates of the students participating in TIMSS 2019 decreased compared to those participating in TIMSS 2015. The change in the correct answer rates was related to the decrease of relevant standards in the mathematics curriculum and tasks in mathematics textbooks. Meanwhile, for tasks about identifying a recursive pattern and representing a covariational relationship, the relevance of the mathematics curriculum materials to the changes in students’ algebraic thinking were not revealed due to the limitation of the small number of related TIMSS items. Nevertheless, it is worth noting that the correct answer rates of students participating in TIMSS 2019 for recognizing recursive patterns and finding appropriate values decreased slightly. Finally, this study makes suggestions for the learning and teaching of early algebra based on the observed results. Keywords: early algebra, algebraic thinking, TIMSS, mathematics curriculum, mathematics textbook