Click the arrow:


Type in @classroom.google.com (To make more labels repeat the same thing with a different email address here)


After Apply a label and create new:


Call this Label whatever you like, This will appear in your panel on the side,


Tick Skip the Inbox, Apply the label and also apply filter to matching conversations,

                                                                       


This will keep new emails from google classroom from appearing in your mailbox and put them in its own label instead.