Abstract
Recently, the phenomenon of students holding simultaneous operational and relational understanding (SOR) of the equal sign has garnered increasing attention from researchers. Investigating this is crucial, as it helps in supporting students’ transition toward a full relational understanding. This study utilised Rasch analysis and student interviews to delve deeper into the SOR stage, involving 1008 Chinese Grade 1 students. The findings validated the SOR stage and uncovered nuanced difficulties, barriers, and contributing factors underlying students’ inconsistent reasoning about the equal sign.