When the Multischool feature was initially released (on 27th January 2016), anyone within Teacher Dashboard who had the role of 'Admin', was also assigned a new role of 'Multischool Admin'. At the time this did not grant these users permission to do anything that they were previously unable to do, but if you had many admins across your school, you may want to check if this level of permissions is still relevant for every Admin.
Administrators are able to create classes, subjects and marking formats across their school. They are also able to change their school's Teacher Dashboard subscription and enable or disable features such as Student Dashboard and AAD Sync.
Administrators are always working in the context of a single school, and have to switch between schools using the school picker in the top left corner. They are not able to perform actions across more than one school from the same interface.
Multischool Administrators have all of the rights of an Administrator, but they also have access to 'Multischool Mode' where they can create new schools, create and assign classes to any schools and manage each school's subscription and features.
When clicking on the 'Multischool manager' they are taken to an overview of all of the schools that are set up on their tenant.
They no longer have to switch between schools, and can perform actions in bulk for many schools e.g.: