This case study investigates, at three Swedish schools, primary school students’ knowledge of the equal sign. The schools were chosen as representatives of schools whose students have different socioeconomic backgrounds. The data consist of Grade 3 and 6 students’ responses to an assessment form based on Matthews et al. (JRME, 43(3):316–350, 2012). A comparison between the schools indicates that there are great differences in the students’ knowledge of the equal sign depending on which school they attend. The Swedish students perform better than South Korean students responding to the same assessment form when it comes to knowing that the equal sign does not mean an operation (“the answer to a problem”). We find this interesting to discuss, as South Korea is one of the countries that performs the best on the TIMSS and PISA.

本案例研究在三所瑞典学校中调查小学生对等号的知识。选择这些学校作为其学生具有不同社会经济背景的学校的代表。数据包括3年级和6年级学生对基于Matthews等人的评估表的回答。（JRME，43岁（3）：316-350，2012年。学校之间的比较表明，学生对等号的了解存在很大差异，具体取决于他们所在的学校。在得知等号并不意味着一项操作（“问题的答案”）时，瑞典学生的表现要好于韩国学生对同一份评估表的回答。我们发现这很有趣，因为韩国是在TIMSS和PISA上表现最好的国家之一。