AP Studio Art Drawing

<p>I really like drawing and I think I'm pretty good, so I want to make a portfolio for AP Studio Art Drawing (for next year of course).
However, my school doesn't offer AP Studio Art, only Art I, II, III, and IV. I haven't taken any of these classes nor do I have room in my schedule until senior year (junior next year). Plus I don't think I'll be able to skip right to Art IV.
So how do I go about doing this? Is the class really necessary to make a good portfolio? Are there any books that can help me?</p>