Are students/users able to join any events they choose?

Ping events are either private or public. 

Public events can be accesses by anyone who wishes to attend. There are no restrictions, but people rarely join an event without a good reason for doing so.

Private events can only be accessed by people who use the event specific link or the event specific pin code. If you have chosen to lock your event, you will need to share either the pin code or the event specific link with the audience whom you want to have at the event. Once you've locked the event and clicked SAVE CHANGES, you can find your pin code in your host dashboard under the Overview tab in the section labeled Access. Later, you'll be able to copy your event specific link under the Attendees tab in the Talent section. 

Overall, most hosts on Ping choose to leave their events set to public and this is always our first recommendation.