Sophie singing Majulah Singapura
In child development center, besides eating, playing and sleeping, a child do learn social skills that will prepare them to a smooth transition when they enter the normal school in Primary one. Some of the activities I am aware of are the standard learning of the english and chinese languages including story telling, singing, drawing, swimming, outings to farms, gardens and performing in the center's annual "graduation" concert (for the K2 Class).
For singing, there are a lot of materials available, even in "Youtube". Try this Sing Along Trailer with your children.