Readiness is a student’s entry point relative to a particular understanding or skill.

Until a teacher learns to use elements like time, space, materials, groupings, and so forth flexibly, it's incredibly difficult to teach students as they need to be taught.

Interest refers to student’s affinity, curiosity, or passion for a particular topic or skill.

We need to understand where are students are at any point during a unit - in other words, what each student actually knows, understands, and can do at a given time based on the content goals we've established.

Differentiated Instruction is a teaching philosophy based on the premise that teachers should adapt instruction to student differences. Rather than marching students through the curriculum lockstep, teachers should modify their instruction to meet students' varying readiness levels, learning preferences, and interests. Therefore, the teacher proactively plans a variety of ways to 'get it' and express learning.

When challenge and skills are in balance the activity is its own reward

Differentiation is simply a teacher attending to the learning needs of a particular student or small groups of students, rather than teaching a class as though all individuals in it were basically alike.