This article reports on the studies of Caroline M. Hoxby, a professor of economics at Stanford University; and Sarah E. Turner, a professor of economics and education at the University of Virginia, who examine why bright students from low-income families do not apply to select colleges. After analyzing millions of records from the College Board, the two economists have estimated that each year, well over 10,000 high-achieving students from low-income families do not apply to any selective colleges, even though such colleges would almost certainly accept them. According to Ms. Hoxby, most such students do attend college somewhere--often at nearby, nonselective institutions whose median SAT scores are hundreds of points below their own. Their absence from the competitive-admissions pool is a problem, Ms. Hoxby said, both because elite colleges ought to be more economically diverse and because the students' own interests would be better served if they chose more selective colleges. Now Ms. Hoxby and a number of other scholars across the country are exploring ways to persuade high-achieving low-income students to be more ambitious when they apply to college. Last year Ms. Turner and Christopher N. Avery, a professor of public policy at Harvard University, surveyed high-school students in Virginia who had done well on standardized tests. Ms. Turner reported that students from affluent families were much more likely to "apply strategically." That is, they were more likely to apply for early admission and to apply to a range of institutions, including a "safety school" and a "reach," as guidance counselors have advised since time immemorial. But not all guidance counselors actually know how to dispense that advice, Ms. Hoxby and Ms. Turner said. Both of their studies suggested that if a high-achieving student attends a rural or small-town high school that does not send many students to selective colleges, that student is not likely to apply to such colleges.