At the close of the fall semester, professors across the country will grade their students. Based on recent trends, those grades will be higher than ever. Around the same time, students will hand grades right back to their professors in the form of teacher evaluations. Those grades, too, will likely be higher than ever.These two facts are very much related. American colleges, especially the most selective ones, are confronting the dual problems of rampant grade inflation and declining rigor. At Harvard, as I wrote recently, the percentage of A grades has more than doubled over the past 40 years, but students are doing less work than they used to. Teacher evaluations are a big part of how higher education got to this point. The scores factor into academics’ pay, hiring, and chance to get tenure. But maximizing teacher ratings is very different from providing quality instruction. In fact, those aims are largely opposed. Faculty are incentivized to lighten students’ workloads and give them better grades, lest they be punished themselves. “To some extent, we are all afraid of our students,” one Harvard history professor told me.Teacher evaluations were born from a reasonable idea: Professors should get feedback so they can improve their instruction. Academics, particularly at national universities, are hired primarily on the strength of their published research, not their teaching prowess. That means they don’t get much direct coaching on how to be a better teacher. In the 1960s and ’70s, students and some faculty were enthusiastic about introducing evaluations as a way to democratize the university. By the 2010s, they had become ubiquitous. Universities ask students to judge their professors on a scale of one to five. Evaluations usually include a range of questions, including whether the teacher grades fairly and makes class fun.The problem is that students are terrible judges of who’s a good teacher. Because learning is not always pleasant, they end up punishing teachers who teach the most and rewarding the instructors who challenge them the least. An extensive body of research shows no correlation—or even a negative correlation—between how students do on objective learning assessments and how they score their professors. One experiment found that Harvard physics students learned more from “active learning” instruction but thought they learned more by passively listening to a lecture. Another study demonstrated that Air Force Academy students who were taught by highly rated professors tended to do worse in subsequent classes.Evaluations are also vulnerable to just about every bias imaginable. Course-evaluation scores are correlated with students’ expected grades. Studies have found that, among other things, students score male professors higher than female ones, rate attractive teachers more highly, and reward instructors who bring in cookies. “It’s not clear what the evaluations are measuring, but in some sense they’re a better instrument for measuring gender or grade expectations than they are for measuring the instructor’s actual value added,” Philip Stark, a UC Berkeley statistics professor who has studied the efficacy of teacher evaluations, told me.Despite their well-documented shortcomings, evaluations matter quite a bit to academics’ careers. “Having been on many promotion and tenure committees, this is one of the main ways, if not the main way, that your teaching is evaluated when you’re being evaluated for a promotion,” Daniel Willingham, a psychology professor at the University of Virginia, told me. Valen Johnson, a statistics professor and former dean at Texas A&M University, told me that evaluations are a “prominent” factor in tenure decisions.Evaluations matter most for graduate students and adjunct faculty, who teach the bulk of undergraduate courses at many universities. The scores can wholly determine whether someone gets hired. “It’s kind of horrifying when you’re an adjunct and your employment depends on a 19-year-old’s evaluation of what you’re doing in the classroom,” Nathaniel Bump, an adjunct English instructor at Georgetown, told me.Even tenured faculty have to pay attention to their scores, unless they don’t mind lecturing to an empty classroom. Some colleges make evaluations available to students as they select their classes. Yale, for example, allows students to filter out courses if they’re rated above a certain difficulty level. Professors with bad ratings will see their course enrollment dwindle. That can affect whether their grad students get teaching opportunities and their department gets new funding and faculty positions.The inevitable result is that faculty feel pressure to cut workloads and pump up the grades they give in order to boost their own scores. In one study, Valen Johnson found that Duke professors could double their odds of getting high evaluation scores by giving A grades instead of B’s or C’s. Melani Cammett, a Harvard international-affairs professor, saw her scores slide when she moved from teaching at Brown to Harvard. After deducing that a cluster of students had penalized her for assigning too much reading, she cut several academic articles from her syllabus and raised the grades she gave. (In hindsight, she told me, she feels she went too far in pandering to her students, and added some articles back in.)[From the November 2024 issue: The elite college students who can’t read books]“Faculty and instructors can basically adjust their teaching style and methodology to help promote higher scores or ratings at the end of the term,” Richard Freishtat, an administrator at Duke’s business school and a co-author of Stark’s, told me. “Especially when they know that’s what’s used to judge their performance and therefore merit, promotion, retention. We’re talking about people’s jobs.” Kim Lane Scheppele, now a sociology professor at Princeton, recalled a former colleague at Bucknell University who would throw parties right before students filled out their evaluations.For many professors, this politicking pays off. At Harvard, as professors in many disciplines have inflated grades, students have inflated their evaluation scores. Amanda Claybaugh, Harvard’s dean of undergraduate education, recalled what one of her colleagues told her: “The equilibrium here is, we give them all A’s, and they give us all fives.”Some professors told me that they ignore their evaluations. Others said they find the feedback useful as long as they recognize the limitations of the format. Willingham, at the University of Virginia, said that he has learned to ignore the hyperbolic comments and appreciates understanding how students experience his courses. And some rigorous but rewarding courses still get strong ratings. But almost no one claims that evaluations actually improve the quality of instruction, which is the main reason for having them at all.Accordingly, some schools are trying to reduce their reliance on them. The University of Oregon and the University of Southern California have both recently switched to a modified review process that pairs student evaluations with faculty reviews of one another’s courses and professors’ own self-reflections. Dartmouth’s engineering program is piloting a similar system. Harvard used to give out a prize to instructors with the best course-evaluation scores. Two years ago, the university began instead rewarding teachers for the strength of their syllabi and their students’ performance in subsequent classes.For all their flaws, however, teacher evaluations are hard to kill. The influential tenured professors with the most power to get rid of them tend not to hate evaluations as much, because the existing system has worked for them, Scott Gelber, an education professor at Wheaton College, in Massachusetts, told me. The alternatives also leave much to be desired. Peer reviews are far more time-consuming than having students click through a survey, and faculty can bristle at being judged by their colleagues. Daniel Shore, the former chair of Georgetown’s English department, summed up the dilemma. “We know that they’re a bad tool for evaluating,” he told me. “But we also need to be held accountable for providing quality instruction.”There’s another reason to keep them around. If universities ever did away with students’ ability to grade their professors, college kids—and their tuition-paying parents—might revolt. Families paying tens or even hundreds of thousands of dollars in college tuition expect the opportunity to critique the service they get. They are, after all, customers. The trouble is that, when it comes to education, the customer is not always right.