The study is based on the theory of teachers' knowledge of students, specifically those who have difficulties learning mathematics, and how their knowledge is expressed concerning students' self-identification. The participants in this study were Namibian high school mathematics teachers (N=6) and their 12th-grade students (N=23), all of whom participated in semi-structured interviews. The students were interviewed about their views of difficulties experienced in learning mathematics, whereas the teachers were interviewed on how they described and identified these students. Participants described their views of school achievement, activeness in class, students' pace, level of asking questions, and math anxiety. The students evaluated themselves, and the teachers evaluated their students. When comparing the responses of teachers and students, the researcher found substantial agreement in how the two groups regarded low achievement in school assessments. In contrast, a low agreement was found regarding student anxiety in learning mathematics. The knowledge and relationships revealed in this study could play a critical role in providing opportunities for teachers to reflect on their knowledge of students, especially when addressing individual students' learning needs. However, this study was limited by a lack of evidence from classroom practice, which could constitute an essential factor in strengthening the findings.