We have designed a science class for improving the pupils' communication ability. In the class, we gave the pupils chances to join a scientific fair for elementary school children, organized by the Hiroshima Children's Museum. The pupils acted as instructors, and we encouraged them to communicate with children, such as question, answer and explanation, as much as possible. Through the activities, the pupils were able to realize the problems in their scientific knowledge, and they were able to enhance the ability of communication as well as that of thinking scientifically. Many children who joined the fair were impressed that the pupils were nice and familiar teachers for them.