From Strength to Strength: Finding Success, Happiness, and Deep Purpose in the Second Half of Life, by Arthur C. Brooks, will debut at no. 1 on the New York Times bestseller list.

That is a testament both to the book’s quality and also to the formidable talents, work ethic, and skill of Brooks himself. The William Henry Bloomberg Professor of the Practice of Public Leadership at the Harvard Kennedy School and Professor of Management Practice at the Harvard Business School has built up a loyal base of fans over the years; already back in 2013, when Brooks was running the American Enterprise Institute, I was suggesting he run for president of the United States.

For Education Next purposes, the interesting part of the newest Brooks book comes from the discussion of professions in which skills accumulate with time rather than decline.

Teaching, Brooks writes, “requires verbal skill and a gift for explaining large amounts of accumulated information. No wonder this field favors the old over the young.” He cites a 1992 study by Daniel Kinney and Sharon Smith, “Age and Teaching Performance.” That study looked at student evaluations of teaching at a single large research university and found “teaching effectiveness appears to improve with age.” It said the impact of age on teaching effectiveness, while significant, “is quite small.”

Brooks writes: “This late-in-life success probably partially explains the professional longevity of college professors.” He mentions one older colleague who, when asked about a retirement timeline, announced “he was more likely to leave his office horizontally than vertically.”

Noting that research productivity tends to decline with age, Brooks writes, “The question is not how to stimulate older faculty to write more complicated journal articles; it is how to adjust their work portfolio toward teaching without loss of professional status.”

This made me chuckle because it was a question that had been identified with remarkable clarity already in the summer of 1952 by the then dean of the Harvard Graduate School of Education Francis Keppel. Israel Scheffler’s 2004 book A Gallery of Scholars recalls the “startlingly original ideas” that Keppel laid out in advance of Scheffler’s arrival at the Graduate School of Education in Fall 1952. As Scheffler recalled it:

The prevalent view, he said, was that the beginning instructor should have the most strenuous teaching load, and that, as he gained experience, his load should be progressively lightened until, with tenure and seniority, his load should be the lightest of all. This prevalent view, according to Keppel, was the exact opposite of the most desirable and rational arrangement. The beginning instructor, who still has to find himself, organize his ideas, plan his original research, and develop a personal style of teaching, needs the lightest load of all. As he continues to resolve these issues in later years, his load may be incrementally increased. The tenured senior professors ought, at their stage of teaching, to be presumed to have worked out all these problems already and should therefore have the heaviest load of all. In line with this conception, he not only wanted me not to teach at all during my first semester, but proposed that I teach only one course during my second, a course of any type, of my own choosing.

A 2016 review by Tara Kini and Anne Podolsky for the Learning Policy Institute looked at 30 studies of the effect of teacher experience on learning outcomes in K-12 education in the U.S. It found, “Although the research does not indicate that the passage of time will make all teachers better or incompetent teachers effective, it does indicate that, for most teachers, effectiveness increases with experience.” The authors note that the gains in effectiveness are especially steep early on in a teacher’s career.

Policymakers trying to take advantage of these findings must grapple with the fact that it’s impossible to become an experienced teacher without first being an inexperienced teacher. That means, unavoidably, exposing at least some students to the inexperienced teachers, too. Perhaps it implies more lateral hires, in which schools or school districts that can afford it hire teachers who gained their early-career experience elsewhere. For individuals getting older, Brooks advises finding some way to share your accumulated wisdom. That doesn’t necessarily mean embarking on a second career as a teacher, though it could mean that. For students with choices, though, Brooks, 57, offers a bottom line: “A note to college students reading this book: enroll in the classes of the oldest professors.”

Ira Stoll is managing editor of Education Next.