The purpose of the Houston Independent School District (HISD) and Head Start Collaborative programs is to share the responsibility for closing the achievement gap between economically-disadvantaged children and their more affluent peers. Currently, HISD collaborates with the following four federally-funded Head Start agencies that serve regional sectors of Harris County within the district's boundaries: AVANCE-Houston, Inc. (AVANCE), Gulf Coast Community Services Association (GCCSA), Harris County Department of Education (HCDE), and Neighborhood Centers, Inc. (NCI). This report compares the academic achievement of kindergarten students who were enrolled in an HISD-Head Start (dual) program to peers who attended either an HISD prekindergarten program, Head Start Standalone program, or neither one of the three programs during the 2014-2015 school year. Highlighted findings include: (1) The majority of students who enrolled in either an HISD-Head Start (dual), HISD, or Head Start Standalone prekindergarten program were identified as economically disadvantaged, at risk and Hispanic; (2) Students who were dually enrolled achieved mean standard scores on the Logramos English language arts (ELA) and mathematics subtests that were higher than those of their peers who were either enrolled in a Head Start Standalone, or had not attended either prekindergarten program; (3) Regarding race and ethnicity, the achievement gap was widest between Black and White students who were not enrolled in either prekindergarten program, with the achievement gap in favor of dually-enrolled Black students on the Iowa ELA subtest; and (4) Students with disabilities (SWD) that were dually enrolled achieved mean standard scores on the Logramos ELA and mathematics that were higher than those of their peers with disabilities who attended HISD or Head Start Standalone programs.