To investigate the sound absorption property necessary to support activities in a nursery classroom, we conducted experiments by installing sound-absorbing materials in the kindergarten classroom. We changed the sound absorption property of classroom in steps, analyzed the change in the sound environment and its influence on activities. As a result, it is suggested that conserving a sound environment supports multifaceted activities in the nursery classroom, and an average sound absorption coefficient of 0.25 or more is necessary to achieve this.