You'll start out as a full teacher, ready to mold little minds. For grades K-12 there are no real levels or degrees of teachers. Any apprentice or assistant work has already been done as a student teacher. Administrative positions in K-12 are a little tougher to come by. It's rare that anyone begins as an administrator without teaching experience.
Most administrators are former teachers.
First, you need to decide whether you want to teach elementary or secondary school. Then you need to choose what state you want to teach in and find out what the degree requirements are for teachers in that state. Then you can plan your course of study. In some states an undergraduate degree in education enables you to teach elementary school, although most states require that you get a master's in five years from your start date. Aspiring secondary school teachers have a few options in terms of preparing for a teaching career.