FILE - In this Aug. 30, 2012, file photo, a tour group walks through the campus of Harvard University in Cambridge, Mass. The Harvard Graduate School of Education is a launching an innovative teacher preparation program it hopes will serve as a national model. (AP Photo/Elise Amendola, File) (Elise Amendola/AP)

As the country debates the best way to improve the quality of teachers in struggling public schools, Harvard University is launching a training program it hopes will serve as a national model.

Starting in January, about two dozen Harvard seniors will begin a three-year fellowship designed to combine pedagogy — learning the methods of teaching from experts — with lengthy practice in the classroom under mentor supervision.

Thanks to $18 million from private donors, who wish to remain anonymous, the program is free to fellows.

James E. Ryan, dean of the Harvard Graduate School of Education, said the university has three goals: improve the quality of classroom teachers in urban schools, create a model that can be copied elsewhere, and present teaching as a viable career to Harvard students and their peers who do not typically think of K-12 teaching in the same vein as law, medicine or business.

“We really want to get Harvard students to think about teaching as a career,” Ryan said. To that end, Harvard is asking its fellows to commit to teaching for five to seven years.

In the spring of their senior year, the fellows will take courses in teaching methods and continue through the summer, with some time spent instructing under supervision in a public school.

“You can talk all you want about teaching, but when you are teaching is when the growth curve is the greatest,” said Katherine K. Merseth, a senior lecturer at the education school who first conceived of the fellowship program more than a decade ago.

During the first full year, Harvard fellows will be placed in schools to teach part time, responsible for two or three classes a day, while working with an on-site mentor, having long-distance coaching sessions with a Harvard faculty adviser and taking an online Harvard class.

“That is a whole lot better than sprinting through the day, teaching five classes, maybe going to the bathroom during lunch, then going home and grading the work of 100 to 150 students,” said Steve Mahoney, associate director of the Harvard Teaching Fellows. “It’s still hard. But it’s doable-hard as opposed to superhuman-hard for a 23-year-old in their first job.”

During the second summer, Harvard fellows will return to the university for more course work and to finish requirements for a teaching certificate. In the second and third years, fellows teach full time but go back to Harvard for retreats, conferences and summer courses. They can take six more credits to earn a master’s degree for about $10,000, compared with about $45,000 for Harvard’s traditional master’s program, Ryan said.

In its design and goals, the fellowship clearly differs from Teach for America, the 25-year-old highly selective program that recruits college seniors on elite campuses such as Harvard, gives them five weeks of training and places them in two-year teaching jobs in some of the most challenging classrooms across the country.

Critics say that Teach for America does not adequately prepare recruits and that the two-year commitment creates instability in schools, as TFA members come and go. The program currently has about 11,000 corps members teaching in 35 states.

“TFA has done an extraordinary job of drawing students into classrooms who wouldn’t otherwise be there,” Ryan said. “But we’re focused on what we know works. A big part is not only the longer prep time but consistent support during the first year of teaching and picking schools that are high-need but also functional. . . . If you want to get new teachers thinking ‘Wow, I can think of doing this for five to seven years,’ their first experience can’t be one of panic.”

TFA officials say that their corps members also have access to online support and in-person coaching by mentors and that while many corps members stop teaching after two years, two-thirds of TFA alumni are involved in education in some way.

But on some college campuses, opponents of TFA have urged students to avoid the organization. At Harvard, an opinion writer for the student newspaper published a piece in 2013 titled “Don’t Teach for America,” and last year, the Student Labor Action Movement urged Harvard to sever ties with TFA.

Nationally, the number of TFA applicants has dropped from about 57,000 in 2013 to 44,000 in 2015. At Harvard, the number of TFA recruits has steadily fallen from 66 in 2011 to 22 this year.

TFA officials blame the sagging numbers on an improving economy and hiring in other fields, noting that enrollment is also slipping at other teacher preparation programs around the country.

Bryan S. Sohn, the TFA recruitment manager for Harvard, repeatedly said in an interview that he does not view the new Harvard program as competition.

“There is going to be overlap in certain situations,” Sohn said when asked if he thought the fellowship program would cut into his TFA applicant pool. “We think that both of our organizations will benefit from expanding the public service consciousness on campus.”

Harvard fellows will be placed in pairs in middle and high schools, Mahoney said. “We recognize that elementary teachers have to be particularly strong in child development,” he said. “They have to teach kids how to read and write, and we’re not ready to tackle that yet.”

Participating schools will include traditional public schools as well as public charter schools, Mahoney said. Program officials are talking with school systems in Boston, Denver, New York City, Dallas, Kansas City, Detroit and the East Bay area outside San Francisco.

Leadership Public Schools, a chain of four public charter schools in and around San Jose, was the first to commit to taking Harvard fellows.

“It’s a very intense program — not just a two-month training — and they’ll have a lot of support, a long program, very in-depth,” said Louise Waters, the superintendent of schools at Leadership. “The level of sophistication and experience you need to be a really successful urban teacher, well, it is rocket science, and it really needs a lot of in-depth preparation.”

Harvard plans to study the fellowship over time. “People are going to want to see how this goes,” Ryan said. “The hope is if this program is vibrant and successful, it will encourage replication.”