Self portraits are complicated. They are never just what the artist sees in the mirror but are a reflection of the artist's character. For me, the most interesting thing about self portraits is that the artist can tell whatever story they want, what the audience sees is exactly what the artist wants them to see.
This concept may be difficult for young artists to grasp but it is an important one. A well done self portrait can tell a story that very few other mediums can express.
The National Portrait Gallery has a lesson on self portraits that is very complete and helps students understand the importance of expressing themselves. The lesson plan uses the tremendous resources of the gallery to show many different types of self portraits and how to talk through them, asking questions that will help students look beyond the face starting back at them.
The lesson plan is geared towards all students, K-12, and can actually be used by all of them. This would be a great way for students in any K-12 classroom to introduce themselves at the beginning of the school year. It could also be used as a serious study of self portraits in a high school level art class.