Instructions to subscribe below!

For Apple:
1) Copy link: 
https://calendar.google.com/calendar/ical/hhcsdstudents.org_classroom2fbad6ff%40group.calendar.google.com/public/basic.ics
2) Go to Settings > Accounts & Passwords > Add Account > Other > Add Subscribed Calendar
3) Paste the link in the Server line.
​4) Click Next & Save

For Google:
1) Copy link: 
​https://calendar.google.com/calendar/ical/hhcsdstudents.org_classroom2fbad6ff%40group.calendar.google.com/public/basic.ics
2) Go to Google Calendar on a Web Browser
3) Click the "Add other calendars" Button (+) > From URL
4) Paste Link

For Android:
All I can find is download Google Calendar on your device and follow the steps for Google above.