Site admins have to explicitly give teachers or other group administrators the ability to customize the layout of group space home pages at the top level node of the class or group space.
To allow teachers to customize their group space home pages perform the following steps:
1.) Navigate to People > Group Manager
2.) Select the top level node for which you want to grant the permission. In the screenshot below, we have selected academic classes.
3.) Select the "Allow admins to customize Group Space Dashboard" checkbox.
4.) Click "Update Settings."
This can be done for each top level node to allow the admins of the subgroups to be able to customize their groups space home pages.