If you want to email your whole class at one time or invite them all to Google Classroom, it is a good idea to create a contact group.
Elementary - you can pretend to “send” an email to all of your students at one time. Before you send the email, high light and copy all of the names in the “to” area. Paste this into the contact box.
Middle School - ask for help in obtaining a list of your email addresses
High School - use the email addresses listed in the High School Data folder
Before you start, copy email address for the desired contact group
To Create a Contact Group
Go to Gmail