In a traditional classroom, the teacher taught one lesson and students were to listen and absorb. While this is certainly the easiest way to do things, it isn't the way things work in a classroom where differentiation is the rule. In a differentiated classroom, teachers assess student levels and provide pupils with specialized lessons at these levels. This may mean teaching a full class math lesson, then re-teaching a key concept to struggling students while others practice the skills featured in the lesson.
In a differentiated classroom, lesson plans pulled from books or reused year after year just won't do. Because teachers must be highly responsive to students' needs to truly differentiate, they must prepare lessons with their specific students in mind. This means that if the teacher's students learn best through movement, the teacher must create a lesson that is movement-rich. Because the teacher cannot simply re-use lessons from previous years, he must constantly re-visit and evaluate past lessons, likely improving the overall quality of his lessons.
While the classic educational practice of lecturing does have a place to differentiation, it is nowhere near as ever-present as in traditional instruction. Because differentiation requires the teaching of lessons at different levels simultaneously, the teacher cannot effectively lecture because, in doing so, she would be teaching down the middle instead of to individual students based upon their ability levels.
Teachers who practice differentiation must assess their students using standardized tests just as classic educator's do; however, in a differentiated setting, the results of these standardized-tests are given much less weight. Because differentiation is all about students reaching their unique potentials, those who truly buy into differentiation don't believe that standardized testing is the proper way to measure student understanding, as these uniform tests are in essence the antithesis of differentiation.