The best way to use Google Classroom and Google Meet on an iPad or Android device (Including iPhones and Samsung Galaxy) is by downloading the following apps. Google Classroom, Google Meet, Google Docs, Google Slides and Google Sheets. All these apps are available in the App Store on iOS devices and the Play Store on Android devices.
You will need to make sure you sign in with the account details provided by the school, as personal accounts wont be able to access the classes setup for your child/ren. If you sign in with a personal account it will ask you to enter a class code which is an indicator that you are signed in with the wrong account.
Hopefully this information will help with your use of Google Classroom.