The teacher has to make every single kid feel that their contribution to the class matters. Students must feel that they cannot afford to miss a single day because the class simply will not be the same without them. This can only be accomplished if if the differences that each kid brings are appreciated and valued. Diversity does not necessary have to mean that you belong to a different nationality or race, though that should be valued too. Every kid is unique and and similar at the same time. Diversity should be accepted and even encouraged at all times. The more diverse a class is, the more learning opportunities there will be for all, including the teacher. When kids are absent the teacher must make the rest of the class genuinely aware of how much absent are missed; consequently no one will want to miss a single class.
Well that is just my short opinion; I hope you can best me.