To only add it to your iPhone, please follow these instructions:
(do not click this link on an Android phone, as you will not receive updates to the calendar – you need to subscribe on a computer via Gmail first for Android phones)

iPhones only:

1. Launch the Settings app on your iPhone or iPad.
2. Tap on Accounts & Passwords
3. Tap on Add Account…then other
4. Tap Add Subscribed Calendar 
5. Paste in the following link (note, if you click the link instead of copying it, it may ask to add the calendar items, do not, instead copy & paste it, to ensure you subscribe to a live calendar):

https://outlook.office365.com/owa/calendar/25d9a3f476794f5ba795dcf67b5db176@bilingualnurseries.com/43650e7a0c5942db8e1333335eaa71e916848776803657575009/S-1-8-2886208624-2411857190-3042927432-2315231751/reachcalendar.ics

6. Click subscribe