If you choose to teach tween and teen students, you'll need to choose a major. This will be the subject you teach. You can get licensed in other areas in many states by adding a minor or taking dual majors in your chosen fields of study. For example, if you want to become licensed to teach high school physical education, most of your classes would be in this area of study with some education classes mixed in. While you will have to meet some minimum requirements for graduation and take other classes, they will be limited in number.
In addition, should you choose a subject such as science, you may need to narrow your focus even more and get a certification to teach a particular study of science, such as Chemistry or Biology.