She has been made an administrator of her school site because she is the Head of the Art Department. She wants to set up a site collection for her department staff. Her school Office 365 working group has decided on a vertical site hierarchy with all sites being subsites of the main site collections for staff and students, and so her new site will be a subsite of the Teaching Staff site collection. Subsites have exactly the same functionality are the same as other SharePoint team sites with.