In G Suite for Education, students and teachers can’t change roles. Only G Suite administrators can change roles. If you accidentally chose the wrong role when you signed up for Classroom, you must contact your G Suite administrator. 

I’m a teacher and chose a student role

Contact your Classroom administrator and tell them to follow the directions to Change a user’s role from student to teacher.

I’m a student and chose a teacher role

Ask your teacher to contact the Classroom administrator. The administrator needs to follow the directions in Change a user’s role from teacher to student.

I’m a student and I want to make a class

Students can’t create classes in Classroom when it's run on a school domain. 

If you want to create a class, for example for a club or a team, you can use Classroom with a personal Google Account. If you’re under 13, you need an adult to create the class.