This post was originally published in @PeterMDeWitt’s blog Finding Common Ground in Education Week. Today’s guest post is written by frequent Finding Common Ground blogger Lisa Westman. Lisa is an instructional coach specializing in differentiation for Skokie School District 73.5 in suburban Chicago. She taught middle school gifted humanities, ELA, and SS for twelve years before becoming a coach. “If we have data, let’s look at data. If all we have are opinions, let’s go with