Middle-schoolers don't crave the approval of people they don't care about. When teachers establish positive relationships with their students, those students become inspired to do well and gain the teacher's approval. They look to the teacher for encouragement, personalized feedback and support. They depend on the teacher's interest in both their academic performance and their personal happiness. With the teacher's attentive guidance and genuine concern, middle-schoolers are likely to drop the apathetic attitude and focus on doing their best.
Students can usually tell when the bar is set low and the teacher expects very little from them. To inspire students to achieve more, raise the bar (but be realistic) and let them know that expectations are high. Don't accept a subpar performance from students; if they turn one in, clearly show your disappointment and reiterate the necessity of meeting expectations. Keep working with students until they achieve the goals that have been set. Stress that students can meet your expectations and refuse to lower them. Your firmness and persistence will inspire your middle-schoolers to keep trying.
Middle-schoolers everywhere know the frustration of having to learn something that seems totally irrelevant. Whether you teach grammar or algebra, your subject is relevant, and students need to know and believe that in order to be inspired to learn it. If you teach history, for example, present it as a crucial tool not only for understanding the present, but possibly also predicting the future. Don't teach historical figures as dead and dry, or as something that happened long before your students were born. Instead, present them as living people who shaped the world your students now live in. Find ways to demonstrate your subject's real-world applicability and your middle-schoolers are more likely to be interested in learning about it.
Every student's learning style is different, and interest can take a nosedive when teachers present material in the same old by-the-book way. Inject as much variety as possible in your lessons - let students get hands-on, use technology, interview people, work in groups or even do independent study. Appeal to as many different learning styles as you can to inspire and engage the most students. Once students realize you will accommodate them with your teaching, you'll earn their respect and likely their attention and good performance.