Let's face it, we are all different. There are no individuals who are completely identical. Variation is inherent in all species. Likewise, children enter school with varying degrees of prior knowledge and life experiences. Therefore, it's imperative that we meet students where they are and work to build upon their strengths and differences. Differentiated Instruction is essential to meet the needs of every student. Yet, this concept is many times easier said than done. It is easy to say differentiate, but where exactly do you begin. Differentiation begins with pre-assessment. You certainly have to know your students; however, knowing your students is more than learning about their  likes and dislikes. It also involves coupling the knowledge of their learning styles with their capabilities to understand the material that you are teaching. Furthermore, when students have not mastered concepts taught, it's important to reteach the skills in way that will essentially help them to mastery. Take a look at one school's success with differentiating in their school. Notice how both collaboration and ongoing formative assessment is the driving force to successfully differentiate for students and essentially help them to truly learn the skills.