An evaluation of the first grade impact of Kindergarten PAVEd for Success (K-PAVE), a kindergarten vocabulary intervention, on children's expressive vocabulary, academic knowledge, and passage comprehension, and an examination of differences in K-PAVE impact by subgroups, based on child assessment and classroom observation data collected from a sample of 65 randomly assigned schools, 130 kindergarten classrooms (2 per school), and 1,296 children