I set up a YouTube account for teachers to use, but I was not able to upload a video until I set the username. However I couldn’t set the username at all. The interface would not work. I would enter my chosen username and click on “continue” and nothing would happen. After searching on the internet a bit, I came up with the solution. I had to enable Google+ use for the sub-organization for that user account in Google Apps for Education. As soon as I did that, I could make the username without any problems. I have heard that it is possible to go back and disable Google+ once the username is made without any ill effects (but I have not actually tried that yet, so I can’t guarantee the truth of that).