For this study, the authors designed an experiment to test whether some high-achieving, low-income students would change their behavior if they knew more about colleges and, more importantly, whether a cost-effective way to help such students realize their full array of college opportunities can be implemented. This was done by randomly assigning interventions that provide different types of information to roughly 18,000 students, including 3,000 students who serve as controls. The most comprehensive form of the intervention, which is called the Expanding College Opportunities-Comprehensive (ECO-C) Intervention, combined application guidance, semicustomized information about the net cost of attending different colleges, and no-paperwork application fee waivers. Expanding College Opportunities Project was designed to to test several hypotheses about why most high-achieving, low-income students do not apply to and attend selective colleges. The application guidance component of ECO-C provides the kind of advice that an expert college counselor would give a high-achieving student. An expert counselor would advise such a student to apply to eight or more colleges, including a combination of "safety," "match," and "reach" colleges. The authors call this group of colleges that are within an appropriate range for a given student's achievement "peer" colleges. Using random assignment of thousands of students, the authors successfully demonstrated that a low-cost, fully scalable intervention can help many high-achieving, low-income students recognize their full array of college opportunities.