When analyzing literature, you still need a thesis in the opening paragraph. For instance, "C. S. Lewis' book The Lion, the Witch, and the Wardrobe is strongly rooted in Christian beliefs." You may use a sentence or two to lead up to that statement, but the point of your first paragraph is to present your thesis. Recounting the high points of the plot are better suited to body paragraphs.
The main difference between college and high school work lie mainly in the level and style of writing. College professors tend to be much fussier about style and format formalities than high school teachers.