The impact of greening schoolyards on the appreciation, and physical, cognitive and social-emotional well-being of schoolchildren: A prospective intervention study

•Children perceived their schoolyard as more natural and attractive after greening.•After greening children reported fewer peer problems and more social support.•Greened schoolyards stimulated girls’ physical activity during one year follow-up.•Improved attention after recess in green schoolyards was found at two year follow-up.•Greening schoolyards seems especially beneficial for girls and younger children.