For some teachers, the LAST and most important step in differentiated instruction is determining what students already know so as not to cover material students have mastered, or use methods that would be ineffective for students. A preassessment can be formal or informal. It can be a quiz, game, discussion, or other activity that asks students to answer some of the questions that would be used to evaluate their performance at the end of an upcoming unit or lesson. It may also be in the form of a learning inventory, such as a Multiple Intelligences inventory (still regarded with skepticism by many researchers), so the teacher will be able to determine how students within the class prefer to learn.

Some models of differentiation do not require a pre-assessment, but rather have students self-assess daily through oral defense, such as in Layered Curriculum. ( Nunley, 2004, 2006)

The goals of differentiated instruction are to develop challenging and engaging tasks that challenge and enhance learning for each student(from low-end learner to high-end learner). Instructional activities are flexible and based and evaluated on content, process and product. This instructional approach and choice of content are driven by the data from students’ assessment results and from the outcomes of other screening tools. Meaningful pre- and post-assessment leads to successful differentiation by producing the results that communicate the students’ needs. Assessments should be used as a tool to create meaningful instruction.