Create a unique username prefix based on unique registration/sign up page

I have a website where people can come and join via a membership and get access to the content. Most of our members are Students and we market to a variety of different schools. We are looking to have a special registration page set up for each school.

The reason behind doing this is that each of our schools wants to be able to track which of their students are signing in and using the features. We are able to run a report in WordPress through Audit Trail and organize it by username.

Therefore, if PSU is the school then we would be able to filter all usernames that start with PSU, delete all of the other users, and put that into a report for our client so that they could see which pages the students are accessing and how often. So we’d want the username to be PSU_LastNameFirstName (or something like that)

The other factor is that the school has paid for 500 of their students to register. Therefore, the students should be able to sign up for free but it’s too much work for the school to input each of their students’ usernames and information – hence the idea for the splash page. Since it’s free to register, we wanted to put the password protection on the splash page so that if someone outside of the school got the link, they wouldn’t be able to register since they would either 1) not have the password or 2) they would create a non-compatible username so I could recognize that and delete them.

Thanks in advance!