use read receipts in your G Suite for Education email to make sure that students have at least seen your messages even if they don't reply to your messages. I do that when I email students to remind them that they have new assignments posted in Google Classroom. That way even if they have ignored the notification in the Google Classroom app or in the automated Google Classroom notification email, I can be sure of whether or not they know they have a new assignment. In the following video I demonstrate the method that I use to make sure students know they have new Google Classroom assignments.
This method isn't entirely foolproof because if a student opens his or her email, I won't get a read receipt. That said, I think it's worth the extra minute it takes me to do this to make sure that more of my students recognize when a new assignment or announcement is posted in Google Classroom.
On a related note, you can speed up this process by using contact groups.