Tablets are becoming increasingly popular in school classrooms. However, ergonomic concerns should be addressed with such use. A particular problem is the reflection of lights on the classroom ceiling onto the tablet screen (glare), which may prevent students from immediately viewing important parts of digital textbooks and cause visual fatigue. Therefore, students using tablets and the teachers instructing such students need to understand this phenomenon. This study created educational material using an interactive three-dimensional computer graphics (3DCG) to enhance the understanding of screen glare during the use of tablets in classrooms. This material enables a comparison of the differences in the visibility of screen glare due to the angle of the tablet and the students’ seating. The results of the evaluation by schoolteachers indicated that the material was effective for understanding screen glare. Since children’s use of digital devices is expected to increase in the future, it is necessary to understand not only the difficulty of viewing when using digital devices due to glare, but also the health aspect, such as reducing visual and physical fatigue.