Effective professional learning requires that staff developers thoughtfully plan to meet varying teacher needs and be responsive to differences--that they model the differentiation teachers will practice in the classroom. Staff developers must be mindful of participants' current learning needs and plan according to their readiness, interest, and learning styles. Understanding educators' levels of proficiency is essential to strategically planning differentiation across a school district. At each stage of proficiency, the learner needs appropriately challenging experiences and relevant support that leads to continuous improvement. This article discusses the characteristics and staff development for the novice, the apprentice, the practitioner, and the expert.