One mistake that students often make is believing that the more effort, pizzazz, etc., that they devote to their work, the higher grade it should receive. Unfortunately, often when students spend too much time on their work or include too many frills, they fail to meet the requirements of an assignment. For example, I teach my students to write for university standards, such as MLA format. After I have devoted a great deal of time explaining and modeling what the first page of an MLA-style paper looks like, I still have students turn in fancy, colored title pages encased in sheet protectors or folders. This is frustrating to me as a teacher because one of the most important lessons I try to teach is that students have to follow instructions. No matter what your major will be in college or which career you choose, you have to pay attention to detail.
As others have said, forget about other students' grades. If your teacher is truly guilty of favortism, you will get nowhere by accusing him of that or by dwelling on that. If you believe that you are completing assignments according to the requirements, then you need to ask your teacher some very specific questions. 1. Do you have a rubric that I can follow so that I can work on meeting requirements? 2. How much time do you think I should devote to this assignment in order to complete it effectively? (For example, if I assign a short essay prompt to prepare students for an AP exam, I tell them that the final product should be something that they could handwrite in 40 minutes or less.). 3. Is individual tutoring available?