The great thing about English/literature classes are there are often ways to bring much of the work up to your own level. In 8th grade, the literature covered generally offers a fair level of depth. There are more opportunities to choose your own reading material and do work based on them. The vocab and spelling focuses on Greek and Latin roots which can be at least interesting. There is a great deal of autobiographical writing and since it's your own, you can be as complex as you wish. Sometimes restrictions actually help you become a better writer.... having to put everything you want to say in 3 pages instead of 6 makes you really determine what is important. Having to pull back on flowery prose can help mature your style. I guess I'd not look at your current class in terms of what it's not giving you and try to decide what you, yourself can dig out of it.
Have you spoken to your teacher? What are your exact concerns? It's not enough to say you are "bored" as plenty of kids who find the class a challenge are likely "bored" too. In fact, I wouldn't let that word leave your lips if you want anyone at school to take you seriously.You need to have an idea as to "why" it isn't working for you. What exactly isn't at your level? Your teacher may have ideas. He/she may give you some insight as to how you yourself can improve the work you are currently doing. They may be able to work with you in areas you've proven high ability. I know it can be intimidating but self-advocating can be quite a successful.
9th grade may offer you something to your liking. It may not. Depends greatly on the school and the individual teachers. 9th grade happened to be my own DD's worst year in English even though it was an honors class specifically for highly gifted students. The teacher (and student teacher) were simply unqualified. However, 7th, 8th and 10th grade were/are fantastic.
You say this was an IQ test, what came of the results? Are you in a gifted program? Are you positive it was an IQ test? I just ask because it's not typical for you to get scores in grade equivalencies. Plus, the equivalencies can be misleading. I'd ask your parents to find out more about the exact test you took. Knowing what the scores actually mean can help you determine how useful they actually are in advocating for yourself. You might also find out if they are part of your permanent file and if they can benefit you in high school placement when the time comes.