This is actually an area that I deal with as part of my work. We usually refer to it as engaged audience. Pretty much every email you receive that isn't a personal communication is tracking your behavior.
Here's a sort of layman's version of what is going on and the limitations.
When an email is sent out through a system that can do tracking a unique ID is added to it. It could just be an integer (e.g. this is email #431312). That unique number is associated in the database with your email address.
A 1x1 pixel transparent image is included in the email. When the server serves that image to you, the link includes your ID and the timestamp from the server is the open time.
If images aren't loaded then the open isn't actually recorded.
It's not possible to know someone read the email (unless there's a quiz.) Click throughs usually stand in for reading even though reading is not required.
The clicked links work in a similar fashion. The links in the email actually go back to the website sending the email to record the click and are then redirected to the final location. You can see this happening in your browser's address bar.
Event registrations happen online and some organizations use the same system for email and event registration, so the data goes into the same database. People running events often have tools integrated into those systems to check in people at events and thereby know if they attended.
It's actually unusual to be able to track the habits of a specific person on a website. If you don't log in, then the website is likely only able to track behavior to IP address or as an aggregate. The exception would be sites where you create an account and log in. For example Amazon knows exactly when and what I'm doing on that site as long as I'm logged in. So if you create an account on a college website, then they could get a history of your activity.
The demonstrated interest sounds exactly like an engagement score which is sort of a hot topic right now. People want to concentrate their efforts on a highly engaged audience. This is one of those 80/20 or four quadrants things.
I think this behavior is less about scoring students and more about prioritizing resources. Schools use basic data analytics tools to optimize work isn't really a lead that gets the clicks.
