As principal of Henry David Thoreau Middle School in Fairfax County, Virginia, Mark Greenfelder has played an instrumental role in building and sustaining a successful professional learning community. His work has helped transform the Thoreau staff into active collaboration, results-oriented practices, and the utilization of consistent intervention systems leading to amazing results. Recently, acclaimed Washington Post columnist and education reporter Jay Matthews selected Thoreau Middle School as a top-performing middle school. In addition, Thoreau was selected as one of only eight middle schools in the State of Virginia as an award winning Governor's School of Education Excellence. Thoreau also received a Teacher Leadership Grant based on its success as a PLC. In addition to being a catalyst for PLC at Thoreau, Mark helped create the ASPIRE assessment system in collaboration with Northrop Grumman, which is a formative assessment system based on his original design. The ASPIRE assessment system was refined and developed by Northrop Grumman and Fairfax County Public Schools, and is being implemented in districts across the country. Mark has experience as a classroom teacher and administrator at the elementary, middle and high school levels, and is sensitive to the needs of children and educators. In every presentation, he shares unique insights on the hard work and collaboration involved in continuous school improvement. Mark holds a Bachelor of Science in Education from Virginia Tech and a Master of Education Leadership from George Mason University. In 2008, Mark was selected as a Top Rated Principal to work for by the Fairfax County Federation of Teachers.