Research has shown that early investments in education have lasting effects. But these effects are greater if there are continued investments from preschool through the K-12 education system. Rucker C. Johnson and C. Kirabo Jackson demonstrate this in their NBER working paper titled Reducing Inequality Through Dynamic Complementarity: Evidence From Head Start And Public School Spending. They look at the way that human capital investments made in preschool complement those subsequently made in the K-12 system.
Their results show that among children from low-income families who are exposed to Head Start, a 10 percent increase in per-pupil spending in K-12 improves educational attainment by 0.4 years, increases earnings by 20.6 percent, and reduces the likelihood of incarceration by 8 percentage points. For other students, the effects were smaller. The same spending increase only improved educational attainment by 0.2 years and increased earnings by 11.7 percent. This provides evidence that over time, such early and sustained investments can effectively break the cycle of poverty.