Better encourage the student to write only what he really loves, and, if necessary, point out individual passages that are overly derivative of specific works, since they distract from the student's own voice. It is important to separate the first phase of composing, where the critical sense must be temporarily suspended, from the later stages, where it must be just as rigorously applied. Entering the critical mode too early is paralyzing. Once large tracts of the work are sketched out, craftsmanship and self-criticism come increasingly into play. The teacher has the psychologically delicate task of balancing encouragement and criticism.
Some students easily become arrogant, or intolerant of other styles.
Since these attitudes close off learning, they need to be discouraged. Other students are insecure, and need encouragement to follow their personal musical tastes, even when they lead in unexpected directions.