High school science teachers are certified to teach only in disciplines in which they have majored or minored. The integrated science major certifies high school teachers to teach in any of the four science disciplines: biology, chemistry, earth & space science, and physics. Integrated science major is also usually required to obtain a minor in one of the four disciplines to go along with their integrated science major. If you wish to teach only a particular science discipline (e.g., Physics), then you may major or minor in just that discipline.
Elementary school teachers in the state of Michigan are certified to teach all disciplines but they are normally required to major in a specific discipline, or to obtain a general major and a minor in a specific discipline. Students at Calvin College often choose to major or minor in integrated science.
Middle school science teachers in the state of Michigan must be certified as either a high school or an elementary school teacher. If you wish to teach science in middle school, then you need to either major in integrated science at the high school level, or you must major or minor in integrated science at the elementary level.