Generally, students are allowed to extend their visas if they are unable to complete the course in the visa duration. However there are conditions that students are required meet before renewing/extending their visa. These may relate to reasons as to why a student was unable to complete their course within the visa duration. The DIBP will make a determination on whether or not to extend a student visa.
Students may also choose to pursue an additional program after successfully completing the initial program, in this case they would apply for another student visa provided they meet the set requirements as outlined above.