Shool will have green yard

Hi. Today I read the news that Tokyo-to decided that the schoolyard of all public elementary and junior high shools in Tokyo will be made of grass. They hope that it will prevent heat island phenomenon. It is the phenomenon of high temperature at small area. They also hope that children will play outside and improve their ability of exercise. I think it is great to have green shoolyard, because it is good for children's body. These days, some school have yard which is made of asphalt. If children play on the yard of asphalt, I think they will have load on their body like knees. However, there is no worry about it if schools have green yard.