Google Classroom is a content management system for schools that aims to simplify creating, distributing and grading assignments. It was introduced as a feature of Google Apps for Education following its public release on August 12, 2014 (Wiki)
Two days ago, Google started rolling out Classroom to all Google Apps for EDU customers. As a followup, the official Chrome Extension for Google Classroom was released today.
I am not sure about what extra features this extension will bring in. There is none mentioned on the Web Store. I will have to wait for someone from my readers to try this out and let me know!
Here is some official literature from the Web Store:
Classroom is a new tool in Google Apps for Education that helps teachers create and organize assignments quickly, provide feedback efficiently, and easily communicate with their classes. Classroom helps students organize their work in Google Drive, complete and turn it in, and communicate directly with their teachers and peers.