The latest development has been a long time coming but is going to be hugely beneficial. When posting announcements, questions or assignments, you can now choose who you post to: all students or selected students. This is now an easy way to differentiate tasks to individuals or groups of students. It means that only those people you select will be able to see the post on their stream, and those in the classroom not selected won't be able to see the post. A great addition.
See more details here, or if you are new to Google Classroom and want to know where to start - check out our training videos here (DRET log in required)