The participation of elementary school students studying in the area is important for the sustainability of the area. This paper is a practice of an elementary school in Tsushima City, an island region of Japan. Two years ago, elementary schools have been conducting river education through collaborative learning. Through river education, elementary school students were able to understand that the river was clean, the extent of the brackish water area was discovered, the river business was understood, and salt damage was understood. We believe that river education will lead to disaster education as a result. Also, elementary school children want the water they use as drinking water to be clean forever, and they can imagine their future life from the perspective of disaster prevention. It was revealed that such elementary school students’ understanding contributes to regional sustainability.