Classroom is an app for teachers, available for iPad devices. Students do NOT have the Classroom app on their iPads.
When teaching in class, you can launch a specific app or website. You can also send documents to and receive them from your students. Finally, you can see which apps students are working in and, at the end of the class, view a summary of how students spent their time.
When you are signed into your iPad using your managed BPS account, you will have access to your rostered Apple Classroom and will see your students in the classes. Students must be signed into their iPads using their school email.