I agree with your comments, MaryAnn, until your final argument with the word "convert." True, it appears to contradict the theme of monasticism, but the poet has already addressed that contradiction through the wearing of the skull, as opposed to rosary beads. As representative of a change in viewpoint, from a boys' world to one that includes the "rite" of the female, I, personally, find "convert" to be a most appropriate word, particularly in the context of this piece.

As for your statement that the poem is "trivial," I suppose that I again will display my ignorance, but is it a requirement that a poem be "ambitious?" The poet has carried his metaphor, chosen his language carefully, written of something that many relate to, and created a work that is, as you say, charming. I'd be happy to do as well.