Student teaching is part of teacher training at most colleges and universities. Individuals who are pursuing teaching degrees are typically required to get student teaching experience in the environment in which they want to teach, such as early childhood, elementary, middle, or high school classrooms. The amount of teaching required can vary among different colleges or universities; some require a semester or more of teaching in a classroom setting, for example. It is generally a required component of receiving any type of teacher certification and completing all the necessary requirements of a degree program, whether it is a bachelor's or master's degree.
The purpose of student teaching is to give potential teachers real world experience, ostensibly to make sure they are choosing the right career for themselves. In addition, it can be added to an individual's resume, and might make him or her more likely to get hired if he really excelled at his work while he was a student teacher. Some students collect letters of recommendation from these teaching experiences to add to a file or resume, which can be instrumental when trying to get hired as a permanent job, or to begin work as a substitute. Many teachers who have recently graduated will need to work as substitutes for a while before getting a permanent position.
The responsibilities given to a student while he or she is student teaching will vary as well. Typically, the student will first spend a period of time simply observing the class and the way in which the existing teacher provides instruction. The student teacher will then likely be responsible for creating lesson plans and activities for the class, and may begin teaching for part of the day. Eventually, the goal is usually to allow the student teacher to take control of the class for a period of time, and be responsible for teaching for the entire day and grading student assignments in order for him or her to get as much actual teaching experience as possible.
Student teachers are not paid for their time, at least while they are undergrads; graduate students completing a practicum may be paid, since they already possess a basic teaching certification. In general, the existing teacher supervising the student teaching will provide an assessment at the end of the student's internship, which will also be given to the student's supervisor at his or her university. This will go into the student's file, and determine whether or not he or she will receive credit for the student teaching experience, or will need to repeat it.