As well as being personal space to sleep, a child's room should be an environment that stimulates creativity, play and thought.
Cut a 30" circle from MDF or plywood (this will be for a double bed, 24" for a single bed). Cut off section of circle so it will sit flush against wall. (Shown below)
Staple drapery fabric to the flat side that will be attached to the ceiling as per diagram. Pleat fabric for fullness. Attach contrasting fabric to flat edge.
Drill holes in plywood and attach securely to ceiling with fasteners. Since this is in a child's room it must be attached securely so it cannot be tugged down. Using fabric glue, attach fabric at edge to cover plywood.
Pull fabric back and attach to drapery tie-backs.