Growth is measured by change in the student. Proficiency is measured by a set standard across the board. Analogy: how we measure runners in a race. We record finish times and award top 10 finishers. In that system, there are winners and losers. But we can also track individual times and measure against past performance. We can celebrate a PR for racers who have improved without judging them against other racers. It makes sense to measure learning by growth and not just comparison. That approach might attract more teachers to schools that are struggling for a variety of reasons (poverty, language diversity, few college educated adults in the household). When ASD pink slipped teachers in the spring, over half of Clarks's teachers were pink slipped. Teachers gravitate toward stable schools with students who come from higher socioeconomic families because their own performance is tied to student performance. Imagine the elevated growth opportunities for teachers in low scoring schools.