The recent renaissance in early computer science education has provided K-12 teachers with multiple options for introducing children to computer science. However, tools for teaching programming for children with wide-scale adoption have been targeted mostly at pre-readers or middle school and higher gradelevels. This leaves a gap for 4 th -6 th grade students, who differ developmentally from older and younger students.In this paper, we investigate block-based programming languages targeted at elementary and middle school students and demonstrate a gap in existing programming languages appropriate for 4 th -6 th grade classrooms. We analyze the benefits of Scratch, ScratchJr, and Blockly for students and curriculum developers. We describe the design principles we created based on our experiences using block-based programming in 4 th -6 th grade classrooms, and introduce LaPlaya, a language and development environment designed specifically for children in the gap between grades K-3 and middle school students.