"Allowing students to decide which grade they wish to strive for, which activities
they will engage in, and how they will demonstrate that they have satisfactorily
completed their studies permits a teacher to seize upon powerful motivating forces
within individual students ... This notion shifts responsibility for learning from the
teacher to the student, but at the same time offers an incentive by insuring success
under known conditions. Students are challenged without being threatened." (Frymier, 1965)