Keeping Your Google Classroom Secure

Google Classroom is a great tool to get information to the students in your classes, clubs, sports, etc.  However, if any student has the code to your Google Classroom and is in your domain then they can join your Classroom.  This can be a problem if you want your stream and announcements more secure.  I just found that you can disable the code option in Google Classroom so that students can only join via invite.