Despite the outcome, M.B.A. headmaster Brad Gioia says he remains fond of Tommy: “I miss seeing him around.”

Tommy Frist and his family provided two of the prerequisites for opening a new prep school: money and land. But there was one they couldn’t buy: top students. Montgomery Bell and the girls academy, Harpeth Hall, had for years tapped Ensworth lower school’s best graduates. Now, like any retailer competing for customers in a niche market, Ensworth administrators embarked on a hard-sell campaign to keep its students from moving elsewhere.

As a flute-playing Ensworth eighth-grader in 2004, Mary Julia Bressman feared that the new high school would cater more to athletes than to arts-oriented students; after all, its first high-profile hire was M.B.A.’s championship football coach. Ensworth administrators pressured her to enroll in the new school. “They’d call our house—‘Maybe there’s something we can do to change your mind?’ ” says Bressman, who held her ground and enrolled at Harpeth Hall. “For a 14-year-old, it was a little difficult to deal with. It put a lot of stress on me.”

The lobbying was “relational” rather than high-pressure, says David Pack, Ens­worth High’s former dean of students. “We knew those kids. The high school was designed with them in mind.”

Alex Peerman, an Ensworth eighth-grader in 2004, says school administrators “gave us the full-court press.” One day, they took Peerman and his classmates to the construction site, where the students ate ice cream while hearing a pitch from the chair of the science department. Demonstrating how materials change properties at low temperatures, the teacher froze a Ping-Pong ball in liquid nitrogen; when he threw it against a wall, it shattered, delighting the teenagers.

Peerman chose Ensworth High. “It’s a coed world, and you should grow up in a coed world,” he says. Peerman proved to be a good get for the new school. As a member of the inaugural class, he helped write the student-government constitution, edited the school newspaper, and was captain of the soccer team. A National Merit Scholar, Peerman now attends Princeton.

Ensworth pushed particularly hard to keep top jocks like promising runner Christian Waddey. Soon after Montgomery Bell’s football coach defected in 2002, he pitched Ensworth High to Waddey’s parents, but the youth had made up his mind to transfer to M.B.A. “We don’t like Ensworth at all,” says Waddey, who now attends the University of Virginia. “They’re trying to imitate M.B.A. and beat M.B.A.”

Sometimes those who left Ensworth felt their ex-classmates’ wrath. Cate Tidwell, like Bressman, opted for Harpeth Hall in 2004. When her freshman soccer team played Ensworth for the first time, she walked over to say hi to her friends on the Ensworth side. “They all started chanting ‘traitor’ to me,” she says. “I had to leave. That brought me to tears.”

Since then, Ensworth High has demonstrated its staying power, succeeding in re-enrolling more than 80 percent of its lower-school eighth-graders. Meanwhile, the rivalry between the two schools has only intensified. At Montgomery Bell, which has seven National Merit semifinalists this year, compared with six for Ensworth, students tend to scoff at its upstart challenger. During an assembly in February, a member of the school’s championship mock-trial team announced that it had vanquished St. Cecilia’s Academy, Father Ryan High School, “and, of course, Ensworth.”

Frist partisans maintain that establishing a coeducational prep school made sense for the city and local business. They say that Ensworth High, strategically located in the heart of Nashville’s fast-growing wealthy suburbs, is an asset for H.C.A. and other firms in recruiting executives leery of sending their children either to Nashville’s struggling public schools or to single-gender private schools.