One of the Yale Admissions Office’s favorite selling points to prospective students — that, unlike at many other large research universities, all of Yale’s tenured professors in the Faculty of Arts and Sciences teach undergraduate courses — is widely believed by students and faculty.

But it’s not that simple. In fact, there is no policy requiring professors to teach undergraduates, and in any given semester, a handful of them, for a variety of reasons, do not.

According to this year’s Yale College admissions viewbook, “100 percent of tenured professors in the Faculty of Arts and Sciences teach undergraduate courses.” Interviews with professors in several departments reveal that faculty members believe this to be a rule. However, Deputy Provost J. Lloyd Suttle confirmed Thursday that no such policy exists.

Indeed, a search on the Online Course Information Web site reveals at least a dozen Yale faculty members who are not teaching undergraduate courses this year. In many cases, Yale College students still have the opportunity to be taught by these faculty members if they enroll in graduate-level courses, and administrators said that (while they do not have formal records) they have not identified any professors who routinely do not teach undergraduates.

Still, admissions representatives often use the idea that professors must teach undergraduates to emphasize Yale’s focus on undergraduate teaching.

“Most of the tour guides when discussing the introductory biology courses will mention that, even at the introductory level, there are Yale’s most renowned professors in the classroom, for example [Nobel laureate] Sidney Altman in MCDB 200: Molecular Biology,” tour guide Matthew Sheehan ’11 said.

While Dean of Undergraduate Admissions Jeff Brenzel said he understands that scheduling conflicts can preclude professors from teaching undergraduates in a given academic year, he said he still believes Yale expects all tenured faculty to teach undergraduate courses.

“Our viewbook states that 100 percent of tenured faculty in the Arts and Sciences teach undergraduates, and we convey that to [prospective students], because that is Yale’s expectation,” Brenzel wrote in an e-mail.

As Suttle explained, ladder faculty are required to teach, but not necessarily to teach undergraduate courses. Teaching requirements are determined within the academic departments, and they vary accordingly, Suttle said.

But members of four departments interviewed said they are also under the impression that faculty members should teach a balance of graduate and undergraduate courses.

“Of course I teach undergraduate courses,” said Altman, a Sterling professor of Molecular, Cellular and Developmental Biology. “It is part of Yale policy.”

Michael Koelle, the director of undergraduate studies for the department of Molecular Biophysics and Biochemistry, said Wednesday that almost all graduate courses in his department are cross-listed as undergraduate courses and enroll undergraduates every year. Koelle added that given this fact, his department is “in line with Yale’s policies.”

Still, the departmental policies, scheduling requirements and the demands of graduate students can all stand in the way of faculty participation in undergraduate courses.

For example, Computer Science professor Julie Dorsey said her department first determines what courses need to be taught each semester before assigning professors. While the department prefers each professor to have a mix of undergraduate and graduate classes, courses will ultimately be assigned to the professors best suited to teach the material, she added.

In some cases, especially in the sciences, a professor’s expertise may be such that his or her teaching is focused more toward graduate students — though undergraduates may still enroll in these courses, as is the case with Yale’s newest Nobel laureate, Sterling professor of Molecular Biophysics and Biochemistry Thomas Steitz.

Steitz, who was awarded the 2009 Nobel Prize in Chemistry last Wednesday, has co-taught a small number of undergraduate courses in past years. But he said his focus lies elsewhere.

“I primarily teach graduate students,” Steitz said.

Of 12 students interviewed, 10 said they think admissions representatives should be clearer when touting Yale’s undergraduate focus.

“It’s a little discomforting that their statements are not always true,” Zachary Weil ’12 said. “It definitely is cool to be taught by Nobel laureates and Pulitzer Prize winners, and so it’s a little sad that we don’t necessarily have access to these people.”

Other students appeared to be more sympathetic.

Taneja Young ’12 said she thinks the most important point is that the majority of professors teach undergraduates, which is not true at many other large research universities. Weil agreed that this was a selling point for Yale.

“ I heard a lot from some of my friends that Harvard cares less about its undergraduates and more about its graduate students,” he said. “I wanted to come to Yale because I knew that Yale put more emphasis on its undergrads.”

Suttle said it shows Yale’s commitment to teaching that faculty teach undergraduates even in the absence of a formal requirement.

As he wrote in an e-mail: “Teaching Yale undergraduates is viewed not so much as a requirement as an opportunity by most Yale faculty.”