(In fact, it doesn't have to be a school as it can create any association with any other record in Student CRM, but the student:school example is a typical and common use.)
How to set it up:
AOD, POD, EVM and MEC: when creating events you will see the panel below. Completing either section is completely optional.
Association Status: you can set it to be active or inactive.
Association Type: you select which Association you want to get automatically applied to every student captured for this event (ie: "used to study at this school") - more about Associations.
With this party: you select which app the other party in the automatic association is in (ie: "Contact Manager:Schools").
Select record: you select the other party, ie: "Glenmoor School (ID: 10457)".
IMPORTANT: this feature associates all students with one school, so it obviates the need to include a "Which School do you study at?" dropdown on your Booking Form, so it is great for events held for just one school. If, however, you want to add a "Which School do you study at?" dropdown - you should use the Automations feature to associate each student with their selected school. This requires you to have a "Which School do you study at?" dropdown on your Booking Form, and an Automation running.