In the Chimney Sweeper (songs of Innocence) the conclusion of the poem would be when he wakes from his dream. He wakes up, gets back to work in the soot, and although it's cold, he feels warm because he knows that if he's good, he'll make it to heaven. You can go a couple different directions with this ending. It can be seen as the acceptance of Christianity in a boy's life. That can be backed up by the references to washing in a river (baptism) and the opening of coffins and setting the boys free (freeing their souls).
Another angle is on the theme of innocence. Little Tom accepts all that he is told. He sees an angel and accepts that. He doesn't question whether or not an angel is real. He just accepts it. He also accepts that he can have God as his father. The beginning of the poem mentions how his biological father sold him. But he accepts God immediately without question. He is still naive. That exploration would be an interesting ending to a paper.