If you are receiving Google Calendar notifications that are unwanted, you will likely have to change YOUR Google Calendar Event notification settings. (This can often happen with shared Google Calendars such as the School Wide Google calendar.)
To adjust your Google Calendar notifications, navigate to Google Calendar making sure you are signed into the account that is receiving the notifications. Find the list of calendars on the left side of the screen. Find the shared calendar that is sending you notifications, hover over the name and three dots will appear. Click on the three dots and select "Settings and Sharing."
Scroll down on the settings page until you get to "Other notifications." Make sure that this is set to "None" to stop receiving emails.
Alternatively, if you no longer need the calendar at all, you can remove / unsubscribe from the Calendar. Find the "Unsubscribe" button at the bottom.