Set up cubbies along one wall of the classroom and assign each student a cubby. That way, he can keep his personal belongings there rather than having them tied to one particular desk. This allows you to change where students sit on a regular basis as they work together.
Arrange the desks in the classroom into clusters with students facing one another. This allows students to interact more easily with each other in cooperative learning tasks.
Arrange chairs at the desks in pairs as much as possible. Having students pair off to teach one another in their areas of expertise is one way to manage a classroom with a wide range of abilities.
Arrange a cluster of desks in a semicircle at the front of the classroom. This allows you to call groups of students up to the front to teach the others in the semicircle, while their classmates work on other projects at their desks.
Create a library area in one corner of the classroom by stocking a bookshelf, and positioning several chairs or cushions nearby. This allows students who have completed their work to go somewhere to read, while they wait for others in the class to get done.
Leave part of the floor open to allow space for hands-on projects that place students of differing abilities together to complete a common task. For example, you might have a group of students work together to set up a miniature city made out of colored paper on the floor.