It is, arguably, important to understand the needs of diverse students so that you can tailor your teaching to meet their needs. There are many people who believe that it is best to try to understand the needs of various kinds of students rather than trying to teach all students in the same way.
It is possible that diverse students will have different needs. It may be that they will not respond to standard instruction in the same way that “mainstream” students do. (However, we must be careful when making such statements because not all students who appear to be “diverse” actually have the same needs as others from their particular ethnic or other group.) Therefore, it will be important to understand what their needs are.
If you understand what they need, you will be able to teach them in ways that are more likely to get through to them. For example, if a student is from a culture that teaches them to keep quiet and submit to authority, you might not want to call on the student very much. It might make them uncomfortable to be made to speak instead of listening to you.
Because diverse students can have different cultural needs, it is important to understand those needs so that you can adjust your teaching style as needed.
Though this question is long past, I need to comment on this as I volunteer at a shelter for homeless youth. Many of these young people are in school or trying to stay there. As a teacher, we need to be aware of the basics of life for the students we teach. Are they sleeping in a car, under a bridge, or couch hopping? Are they safe where they are? Do they have food to eat or clothes to wear? Do they have any place to get clean or wash what clothes they carry in their backpack? Are they exhausted because they were awake all night trying to hold onto what little they do have? Does anyone at school know what they are going through? I believe that the above answers are good for teachers to think about; I also believe that as teachers we need to be looking for signs that our students do not have even the basic necessities of life so that learning can happen.
It is important to understand the needs of students to best teach them. As previously pointed out, knowing the cultural, educational, and social background of a student can help you effectively reach that student and keep them engaged and active in the classroom without potentially causing offense. For example, if a student is not a native speaker of English, they might be nervous to read aloud, thus raising their affective filter. Some students do not respond well to environments in which the teacher is not the authority figure. All students have different needs, even within the same "type" of students. A student's home language, emotional well-being, learning style, culture...all of these factors influence learning.