“SimRiver” is a type of simulation software. It was developed for students to increase their understanding of the relationship among human activities, river water quality, and diatom communities. We applied “SimRiver” in four classes, namely, two high-school classes, one junior high-school class, and one extramural class for junior- and high-school students, and analyzed the reactions of students via a questionnaire survey. The results indicated that many students preferred to study with the simulator. Although the students were unfamiliar with diatoms and beginners in micro-organism classification usually find it difficult to identify diatoms, the built-in identification support system of “SimRiver” simplified the identification process and the students accomplished it in a short time. The use of this interactive educational tool motivated the students and increased their understanding of the purpose of learning, regardless of their age and academic performance. However, TWINSPAN analysis indicated that nearly 40% of the students did not demonstrate an interest in the learning content, because they were interested only in the simulator. It is necessary to direct their attention to the original aim of learning with the simulator. Further strategy for improving the class is discussed with the use of information technology.
