Researchers have found a group of children who attended an intensive childhood education program from preschool to third grade were more likely to achieve an academic degree after high school, compared to a similar cohort that received other services. The findings of a 30-year study of students who attended the Child-Parent Centers (CPC) program in inner-city Chicago appears in JAMA Pediatrics. 

This study suggests that particular elements are more successful in early childhood intervention programs than others. According to the National Institutes of Health (NIH), who funded the study:

The CPC program provides intensive instruction in reading and math, combined with frequent educational field trips, from pre-kindergarten through third grade. The program also provides parents with job and parenting skills training, educational classes and social services. In addition, the program encouraged parents to volunteer in classrooms, assist with field trips and participate in parenting support groups.

Graduates of the CPC program, on average, completed more years of education compared to students who participated in other early intervention programs, and are more likely to achieve an associate's degree or higher. A previous study also showed these CPC graduates to have higher incomes, lower rates of crime and incarceration, and lower rates of depression.

You can read more about this study on the NIH website.