At ubbu, when you create student accounts the platform automatically generates usernames made up of words and numbers. At the moment ubbu doesn't allow you to change student usernames, but as a teacher you can change your students' usernames.
To do that, click on Classroom Management and then on the button marked on the image below.
Then, click on the Generate username button and then Confirm.
In addition, to make your teaching experience easier, it is possible to link the real names to the usernames, and store them in encrypted form.
To learn more, see the article Connecting your students usernames with their real names.