As you may have noticed, the portraits added in a portrait section are sorted alphabetically. This can be a bit confusing when you see a teacher's portrait image in the middle of the page, but there is a very quick solution for moving this image so that it is the first portrait for the section.
To do so, open the desired portrait section. Find the teacher's portrait you want to move in the media tray (found along the bottom of your screen). Drag and drop the portrait image to the desired spot on the page. Notice all students will shift one space over to make room for the teacher portrait.