Although the Every Student Succeeds Act sets the parameters for parents and families to be involved in their children's education, there are no specified guidelines on how that involvement should be designed to best impact student achievement. The purpose of this study was to compare Grade 3-5 students' mean Milestones test scores in English Language Arts, mathematics, and science (dependent variables) at two Southeastern United States elementary schools which offered parental involvement/parental engagement programs--a nonmandatory or mandatory program (independent variable), represented by School A and B, respectively. The theoretical foundations of the study were the social and human capital theory and the school, family, and community partnership framework. The seven research questions compared student achievement scores for Grades 3-5 English Language Arts and mathematics and for Grade 5 science between schools. A quantitative design, using ex post facto data from the 2018-2019 school year (n = 1076), included seven independent samples t tests to determine statistically significant differences in mean Milestones test scores among students at School A and B. The results indicated a significant difference in all three grades, across all three subject areas. Students from School B with the mandatory parental engagement program experienced higher achievement in all subjects than students at School A with nonmandatory engagement. These results support the need for mandatory parent involvement programs that guide parents in how to support their children's achievement. This study may contribute to positive social change by encouraging educators to promote new strategies and partnerships with parents and families specifically designed to improve student achievement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]