1. Go to "staff"
2. click on the staff to share calendar with
3. click on Calendar sharing
4. click "Share"
5. click "Copy" to copy the link of "Shared Calendar"
6. send this link to the teacher.
For the teacher, after receiving the link, they could subscribe to the calendar according to their own calendar service and follow instruction below :
1. Google calendar
https://support.google.com/calendar/answer/37100?co=GENIE.Platform%3DDesktop&hl=en
2. Mac iCal