When you use your mobile phone, it may be a bit tricky to log-in, especially if your phone uses the Google Playstore. Your phone will have already been set up with your personal Google account and your first step will need to be adding your school account to your phone. Watch the video to see how you might be able to trouble shoot any issues that you come across when logging into your school's account for Google Classroom.
How to Login to Google Classroom on an Android
How to Login to Google Classroom on an iPhone