You can share your calendar on Office 365 with other staff in your School, go to the calendar by selecting the calendar icon at the bottom left of the screen in Office 365 Outlook (https://outlook.office.com/):


Select share from the menu at the top of the screen:

You can then enter the email address of the person you wish to share your calendar with (1) and change their permissions e.g. whether you want them to edit you calendar or just see when you are busy (2):