Communication has long played an essential role in many fields of life. In education,
communication competency is one of the main competencies that need to be built and
developed in the teaching process. Many studies worldwide have provided a way to assess
communication competency in traditional classrooms, but there are very few evaluation
studies in online classes, especially in Mathematics. This paper presents a case study
assessing the levels of mathematical communication competency in online classes of high
school students in Vietnam. Interactive conversations between teachers and students are
recorded using Zoom, an online teaching software, and analyzed by ATLAS.ti – a widely
used and accessible tool in text mining. The research also provides a qualitative analysis
about the assessment levels of mathematical communication competency and challenges in
online learning.

Keywords: Mathematical communication competency, online class, high school,
ATLAS.ti.