Primary

From HymnWiki

The Primary is a children's organization (ages 3 to 11) in the LDS church, much like a Sunday School for children. Much (far from all) of the time taken during primary is used singing and learning primary songs.

Currently, Primary is held once a week, on Sundays, during the same time adults (ages 18+) go to Sunday School. There was a time when it was held some time during the week, rather than on Sunday.