In the built in calendar for Mac you are able to subscribe to the calendars for school. 

From the 'File' menu select 'New Calendar Subscription' or by using the ⌥⌘S

Enter the URL in the box that appears

The calendar details should populate if you'd like to adjust them do so now.

(i) If you'd like to sync it to your iPad/iPhone you can change the 'Location' to iCloud.

URLS for the calendars;
School holidays
PE Fixtures

Staff can request the Staff URL from the helpdesk.