Proponents of personalized learning say that many elements of curriculum, assessment and instructional design must be present in classrooms for students to succeed and often use software systems to manage and facilitate student-led instruction. Proponents argue that classroom learning activities must build upon students' prior knowledge and teachers need to allocate time for practice. Advocates argue that teachers must continuously assess student learning against clearly defined standards and goals and student input into the assessment process is integral.[8][9][10]