Every Monday, Tuesday, and Friday at 8:39 a.m., Tony Mao files into his sophomore-level University of Connecticut engineering course in applied mechanics. Mao is not a university student. He’s a high school senior at the private Christian Heritage School in Trumbull, Conn., who spends his free time playing on the coed varsity tennis team and writing college application essays.

Part of a skyrocketing number of students attending high school and college simultaneously, Mao (who got a perfect score on the SAT in math) plans to use the courses so he can skip ahead on his route to a career in architecture.

But it’s not just precocious high achievers like Mao who are benefiting from this phenomenon that is most often referred to as “dual enrollment” but is also known as “dual credit” or “concurrent enrollment.” Increasingly, educators and other advocates are touting dual enrollment as an effective way of helping underserved students—including first-generation college-goers, low-income racial minorities, and even dropouts—to obtain a college degree.

And while questions remain about access and quality, evidence is accumulating that students who take courses for college credit while in high school are more likely to go on to college, stay there, and ultimately graduate than classmates of similar backgrounds and abilities who follow the traditional high school path.

People assume that taking college courses while in high school “is only for top students in really good suburban high schools. But it’s not,” says Ben Byers, associate vice president for operations at Gateway to College, a nonprofit organization that places dropouts and those on the verge of dropping out in special programs on 43 college campuses across the country, where they take college and college prep courses.