Are you or your students having trouble accessing Google Forms, Drive, or Classroom when it requires you to be logged into your school gmail account? Here is my guide to fixing/avoiding these issues.
The first and simplest method is to use a Chromebook if possible. Just have the student login to the Chromebook with their school account. That should eliminate other logins interfering (Unless you have multiple logins in that Chromebook browser. If so delete the extra account.).
The second way is to create a separate Chrome Browser login desktop icon on your PC. Check out the video below to be walked through that.