A summer substitute teacher fills in for the full-time teacher and instructs students during summer school programs. In this role, you may work for one particular school district and travel to different schools within the district that have vacancies for the day, or you may be on the list of substitute teachers for multiple school districts. Your specific job duties vary, depending on the grade and subject you teach. But the primary teacher often leaves a lesson plan for you to follow and instructs you on what assignments need to be completed that day. You must also keep accurate student records and document activities to inform the primary teacher of the day's progress.