Both students and parents can access Google Classroom from anywhere, including from their phones, when they download the Google Classroom app for any Smart Phone product. 

Yes! Teachers definitely use Google Classroom for parent and student communication. This year, your child's teacher will use Google Classroom for communication.  Each teacher will send you an invitation VIA EMAIL, and after accepting, you will receive updates directly from them, which may include information on upcoming or missing work and announcements. You can even see grades, request data documents, and even schedule parent conferences!