To add a school holiday calendar, please go to → Calendars & Task lists section and a) add the calendar directly from the calendar list:
Hint: If you happen not to find a suitable school holidays in our list or look for other special calendars, you will need to use other sources. There are two easy ways of doing it:
1. You could profit from our content app. To do that just search for "Premium Calendar Store" in Play Store. Once you've downloaded the app, click on "Subscribe" and add any calendars you're interested in, such as the school holiday calendar. The events of the subscribed calendar(s) will then be displayed in your calendar app.
2. You could use the → "Import/Export calendars" function and simply import the priorly downloaded calendar file into the app. The calendar file (.ics, .ical) with the school holidays needs to be found online and saved on your Android device.