You need your Google Apps for Education account information—email and password—to sign in to Classroom. A Google Apps for Education account is a unique account set up by your school and looks like email@example.com.
Note: You can’t use your Gmail or any other personal email account to sign in to Classroom. If you don't know your account details, ask your school’s IT or Google Apps administrator.
Remember: Your Google Apps for Education username looks like firstname.lastname@example.org