Sentral Calendar has ical/ics support, and this can be used to view your Sentral Calendar in School Stream.
Important to Note
To modify Sentral's Calendar preferences, you need to be either an Administrator or the owner of the Sentral Calendar you want share.
To enable a Sentral Calendar to be synced with School Stream, you need to ensure that the following has been setup.
Login to Sentral and use the module menu to go to the Calendars module
Click the name of the calendar you wish to share publicly
Click the Preferences button above the calendar
Update the View Privileges setting to be Open: Anyone (note that this will mean anyone with the link will be able to see the entire calendar)
Click Return to Calendar
In the browser's location field, append the text below to the URL
Copy this whole URL and share it with School Stream support email@example.com who can assist with adding the url to your app.
An example of this would be
Please note: the URL should be the publicly accessible URL, which in your case would be using the school's Reverse Proxy address of http://sentral.schoolname.edu.au/webcal... and not any internal school-only links, such as http://18.104.22.168/webcal/...