<p>Teachers’ reflection is essential for improving classes. However, it is costly to introduce sensors into daily classroom environments, and collecting and visualizing data has always been challenging. To address this issue, this study aimed to clarify to what extent the daily learning log data from multiple learning tools can be used for classroom activity visualization. Learning activity visualization with Learning Analytics techniques is the emerging approach to supporting reflection and improving learning practice. However, the captured activities by data were usually limited within each tool, and it was difficult to capture the overall class activity. In Japan, environmental advancements have led to the solution to this problem. The Ministry of Education distributed one device per student. It introduced a standard model for learning tools that supports Learning Tool Interoperability and eXperience API (xAPI) to improve educational data interoperability. This study proposed to utilize these cross-platform integrated learning log data for learning activity visualization. A case study of a Japanese junior high school class with 38 students and a teacher’s xAPI log showed the possibility of not only visualizing what happened in the classroom from the learning logs that are accumulated on a daily basis but also revealing why it happened. This study showed the potential for big data in a standardized format from the smart learning environment to capture the lecture process, which will contribute to making data-informed reflection part of daily practice.</p>