Deleting a Lessons subpage is a two-part process. First, remove the link to the subpage from the top-level page and then delete the subpage from the site.
If you titled your page something other than Lessons, select the title of the page as it appears in your Tool Menu.
Click the Delete icon next to the subpage to be removed.
Click Delete again to confirm.
You will see the list of pages with the unused pages listed at the bottom. Only items that are not linked from any other location can be permanently removed from the site.
Click Delete selected pages to completely delete the selected page/s from the site.