In this technical report we document the development and piloting of the Learning Receptiveness Assessment (LRA) Greenhouse for Prekindergarten. This technological tool was designed to prevent reading disabilities by supporting effective "assessment-guided instructional decision-making" by Preschool teachers. The LRA Greenhouse comprises a tablet-based formative assessment and app-enabled research-based intentional teaching activity plans, monitoring checklist, and reports; it also includes a support website containing printable curriculum materials, online training modules, and teacher resources. The LRA measures emergent prereading skill levels, classroom behavior regulation, and working memory processing capacity in the fall, winter, and spring to provide teachers with multi-dimensional information for addressing children's "high priority needs" in time for Kindergarten. Activity plans focus on building children's literacy and behavior regulation for managing social-emotional and task engagement experiences, which are crucial to adequately develop during the Prekindergarten-Kindergarten transition as children adjust to classroom-based learning. We share our development process, descriptions and screenshots of wrap-around supports and features, as well as findings from two pilot studies conducted across 12 classrooms. Our goal is to present lessons learned from developing a technological tool intended to feasibly and sustainably "bridge a gap" in reading disabilities prevention between early childhood and K-12 schools, and preliminary evidence of positive impact for both Prekindergarten children "and" their teachers.