Obviously, the first draft of your portfolio is not going to be the final one. But the audience won't have seen those first drafts and they won't understand how artistic development has affected and fine-tuned the final pieces you put forth for viewing. Artistic processes involve expanding on your prompts and adding facets that an audience will need to understand to realize why the version you put forward is the version that you chose.
Audiences typically can recognize what a piece is made of, but communicating these changes and experimentations and their purpose to an audience can be difficult. Here are some reasons that may stick with you as to why you chose a specific material; these may be helpful for your artist statement or any presentation of your work.
Achieve a desired effect: Mixing different mediums can create unique textures, layering, and blending that might not be achievable with a single medium. Wanting to make your work more complex can explain the addition of one or more media.
Express individuality: Artists often mix mediums to create a style that is personal and distinct to them. A material or item you used may be personal or special and communicating that is important.
Challenge oneself: Mixing mediums can be a way for artists to push their own boundaries and experiment with new techniques. This could speak to your improvement throughout the school year and how this portfolio is a culmination of what you've achieved.
Communicate a message: Artists can use different mediums to convey multiple ideas or emotions in a single piece of art. There could be a specific material responsible for a certain motif or message.
Create a specific aesthetic: Mixing mediums can result in a visual style that is difficult to achieve with a single medium. Getting to be more aware of your specific aesthetic as an artist is vital to improvement, and the audience wants to react to that.
In terms of your revisions and redoes, as well as the idea that fueled your project, demonstrating the usage of these is entirely up to you. It has to be personal, relevant, and concise while still teaching an audience about the artistic identity of you and your portfolio.
Demonstrating that you've used practice and revision in your art may be difficult since you are only showing your audience a final version of each work. Though, in any written statement, it is important to talk about how your creative approach and problem-solving changed while you attempted to complete the portfolio. Not necessarily how many tries it took, just what changes you made and why they were effective.
The same goes for ideas; start with where you were at the beginning of the year and concisely explain how that idea morphed the more you worked at it. No artist's idea is ever the same from beginning to end, so it will only benefit you to fully understand the ways in which your idea changed and how that improved your art-making.