Colorado has seen a growing gap in the achievement of poor and low-income students compared to their more affluent peers. A widening achievement gap has short- and long-term implications for children, as well as the state. Research suggests that high-quality early childhood programs are an effective way to reduce or even eliminate achievement gaps. The Colorado Preschool Program (CPP) is an example of such a program. It has proven to be very effective in closing achievement gaps and preparing children to enter school ready to succeed. This Policy Brief estimates the impact that eliminating CPP would have on the achievement gap. Eliminating CPP would potentially increase the achievement gap between low-income students and their more affluent peers by 3.8 percent to 7.7 percent. The proficiency rates of both low-income and more affluent students would decrease if CPP were eliminated; but because three out of four of the children served by CPP are low-income, the decrease in the percent of students passing the test would be far greater among the state's low-income children. Overall, eliminating CPP could possibly increase the number of third graders that do not reach proficiency on state assessments by more than 3,000. (Contains 4 tables and 10 footnotes.)