Purpose: This study examined (1) the causal impact of Head Start on children’s comprehensive outcomes and (2) why families did not comply to the original assignment. Method: Based on the Head Start Impact Study data, children between the ages of 3 and 4 years (N = 3780) were examined for assignment, attendance, and causal impacts on outcomes. Results: Effect of instrumental variable analysis was greater than that of assignment and attendance for measured outcomes. Assignment to the Head Start, older child age (age 4 over age 3), urban residence, and higher family income were associated with non-compliance. Inclusion of care quality into the model illustrated important nuances in predicting families’ compliance with Head Start versus control condition. Discussion: Head Start participation among low income children should be maintained for its positive causal effects on children. Quality of childcare as well as several child and family barriers to access to Head Start needs to be addressed to enhance Head Start enrollment.

目的：本研究检查 (1) Head Start 对儿童综合结果的因果影响，以及 (2) 家庭不遵守原始分配的原因。方法：根据启蒙影响研究数据，检查 3 至 4 岁 ( N = 3780) 的儿童的分配、出勤和对结果的因果影响。结果：工具变量分析的影响大于分配和出勤对测量结果的影响。分配到启蒙教育、年龄较大的儿童年龄（4 岁以上 3 岁）、城市居住和较高的家庭收入与违规行为相关。将护理质量纳入模型说明了在预测家庭对 Head Start 与控制条件的依从性方面的重要细微差别。讨论：低收入儿童的启蒙活动对儿童具有积极的因果影响，应保持其参与。需要解决儿童保育质量以及儿童和家庭获得启蒙教育的若干障碍，以提高启蒙教育的入学率。