Login Form for visitors

I teach a class where I share my webpage to the students on the links and tools that I teach. I do not want these open to the public so I have password protected the page. What I would like to do is create a login form that users put their last name in and then the password they are given at the class. I also want to be able to have multiple passwords for this form. My reasoning is I can see who is using the page and what class uses it the most. Is there a plugin or any help creating this would be greatly appreciated. Thanks in advance