Goodman Research Group, Inc. (GRG) conducted a summative national field test study of the PEEP Explorer's Guide in early childhood education (ECE) classrooms. Participating teachers used four-to-six Explorer's Guide Units with their students over the course of one school year. GRG assessed changes in teachers' science-teaching practices after using the PEEP Explorer's Guide over an extended period of time and examined potential barriers to using the PEEP Explorer's Guide throughout the course of a school year. The evaluation sought to measure the following professional audience impacts and