If you want to hear about the power of a worth-while mission, you might talk to a nun. If you want to understand how to create shareholder value, bolster your customer base, and create a culture of innovation, you might talk to a Yale MBA. Or you could save some time by talking to Sister Barbara Rogers. A nun with an MBA from the Yale School of Management, Rogers has managed to lead a faltering, tradition-bound institution through strategic and operational changes by focusing on mission and values.

Rogers, 47, is headmistress of an all-girls school called Newton Country Day School, one of the 130 Sacred Heart schools located all over the world. Housed in a gothic mansion outside of Boston, Newton Country Day is an old place full of modern surprises: It's not uncommon to see a group of students sitting on pillows in a dark-paneled room -- doing their homework on laptops.

That scene is a far cry from the school that Rogers took over in 1989. That year, the school had a $160,000 deficit, and enrollment was declining (it hit a low of 156 students in 1992). Since Rogers took over, the endowment has increased more than sixfold. Enrollment has risen to 280, and construction on both a new arts center and a group of new science labs will begin next month.

This turnaround is a case study in how a basic sense of mission, rooted in a set of enduring values, can become an engine for fast change. "Being clear about our mission gives us the freedom to change," says Rogers. "It also gives us the ability to make decisions quickly. We're not capricious, but we're free to be unpredictable."

How did Rogers lead such a transformation? By dusting off a long-neglected set of five goals that the school had adopted in 1975. (The goals originally came from the "Plan of Studies" that was drafted by the founder of the Society of Sacred Heart in 1805.) Rogers decided to use those goals to legitimize tough changes, to build consensus among staff members, to raise standards, and to boost morale. "We put the goals first and formed our actions around them, even though that may have seemed financially irresponsible at the time," she says.

Take goal two, for example: "a deep respect for intellectual values." To Rogers, that means leaving a slot open, rather than accept an applicant who doesn't meet the school's newly rigorous admissions standards. In the past, that has also meant offering an advanced-placement course in physics, even though only three girls chose to participate in it and even though the school was low on funding. Or consider goal four: "the building of community as a Christian value." That means diversifying the student body by increasing financial aid and by providing transportation so that girls from disparate areas can participate in after-school activities. (The number of minority students has grown over the past decade from 17 to 54.) "How did we afford to do all of this?" asks Rogers. "We couldn't afford not to do it."

One of Rogers's earliest moves as headmistress was to revise the school's awards policy. Before she took over, every girl in the school received an award of some sort: Commendations were doled out for such accomplishments as athletic achievement, an outstanding English essay, and improvement in math class. "The girls couldn't have cared less about the awards," says Rogers.