Hi Steven,
I'll give you an example of these service item type.
Item001 (Package) contains of
Item001-A (Course)
Item001-B (Course)
Item001-C (Course)
When I open sales order, I will choose Item number as Package, then I will explode BOM to extract 3 courses as child-node of Package.
Condition: All item are set as Service item type, because the meaning of Item is all about Education course.