Adam Grant is an organizational psychologist at the University of Pennsylvania’s Wharton School. He authored “Hidden Potential” and “Think Again.” He also hosts the TED podcast “Re: Thinking.”

A few years ago, I started asking lecture halls filled with students to raise their hands if they had run out of time on the SAT. In each room, nearly every hand went up. I was surprised, but I shouldn’t have been.

For decades, educators have seen speed as a marker of aptitude or mastery, forcing students to scramble to finish tests. But a race against the clock doesn’t measure knowledge or intelligence. It assesses the much narrower skill of how well students reason under stress. As a result, timed tests underestimate the capabilities of countless students.

New evidence shows that although smarter people are faster at solving easy problems, they’re actually slower to finish difficult ones. They’re well aware that haste makes waste, and they don’t want to sacrifice accuracy for speed. You wouldn’t want a surgeon who rushes through a craniectomy, or an accountant who dashes through your taxes. Even for the many jobs in which people are judged on speed, there’s no evidence that doing algebra under time pressure is useful preparation. Although it pays to be quick, it also pays to be determined, disciplined and dependable.

Strangely, though, the tests that define students’ grades and help determine their educational and professional fates are rarely designed for deliberation. They evaluate students as if they’re applying to join a bomb squad or appear on “Jeopardy.” Time pressure rewards students who think fast and shallow — and punishes those who think slow and deep.

One fall, one of our daughters was pleasantly surprised by her grade on a math midterm. Despite being the longest and hardest test of the semester, it was her highest score. At first we were puzzled: She hadn’t changed her study habits or made a quantum leap in understanding. Then we learned that it was the first test where she didn’t feel pressed for time. Her teacher had allowed more time per question than usual.

On math tests, one of the few skills in which boys consistently outperform girls is mental rotation — turning 3-D shapes in their minds. But gender differences vary dramatically based on time pressure. Across several dozen studies, the more time students had to finish tests, the smaller the female disadvantage became. Shifting from short time limits to no time limits — or even just allowing more than 30 seconds per question — was enough to cut the gender gap in half.

It’s well known that the “girls can’t do math” stereotype can cause female students to underperform on math tests. The fear of confirming the stereotype can lead to test anxiety, draining working memory and disrupting cognitive processing. What we’ve overlooked is that time pressure can exacerbate these effects. When girls are distracted by doubts about their abilities, it takes them longer to finish problems. Having to rush leaves them more prone to choosing suboptimal strategies — and to possibly making mistakes. Even if they’re not anxious, female students tend to work more methodically than male students. When they have more time, they can rethink their approaches and double-check their answers. They also become more comfortable making educated guesses.

I tried this out with our daughter on practice tests at home. She’s an honors math student, but when she was under time pressure, she made distracted mistakes like plugging in the wrong formula on relatively easy algebra problems. It was the math version of a typo, and we ended up coining a term for it: a matho. But when there was no time limit, she excelled on difficult algebra problems — and mental rotation, too.

Time pressure doesn’t just underrate the math abilities of girls and young women. Having to hurry can obscure the abilities of anyone who has reason to worry. That might include boys who are expected to underperform in reading, immigrants who are doubted on verbal aptitude and Black students who face a host of questions about their intellect. It also includes students with learning difficulties such as dyslexia and ADHD — or mental health conditions, physical disabilities and sensory impairments.

A common solution to this problem is for schools to offer extended time to accommodate students with disabilities. But lately, this has created an accommodations arms race as parents and students try to game the system to get diagnosed with a learning difficulty or health condition. Why not give everyone enough time to complete the test?

I heard from one counselor in the Northeast whose high school experimented with extended time for final exams. After allotting four hours instead of two, they were bombarded with complaints. Students who had previously met the requirements for special accommodations — and their parents — said they ran out of time. Why? The teachers wrote longer exams to fill the space.

This madness has to end. If a significant portion of the students run out of time, it means the test is too long or the time period is too short. That’s why, as soon as I read about this evidence, I started writing two-hour exams for the three-hour exam period allocated to my class. But many other educators still cling to the fraternity hazing excuse: I had to walk five miles barefoot up a snow-covered hill, so you should suffer too! Most teachers, though, say they’re preparing their students for the pressure they’ll face in standardized tests.

It’s a delicious twist of irony, then, that the lifeboat to rescue us from the tyranny of time pressure is being piloted by the folks behind the mother of all standardized tests. I learned recently that the College Board has redesigned the SAT to minimize time pressure.

Historically, the SAT gave students “too much to cover and not enough time to do it,” the College Board’s chief executive officer, David Coleman, told me. But developing a digital version gave them the opportunity to experiment. And the results were so impressive they decided to stick with them. Starting next year, the test is shorter overall, and most importantly, “on average, 97 percent of students complete all questions in a section with up to seven minutes to spare on each section,” Mr. Coleman said. “It’s time we stop confusing quick with smart.”

This could be game-changing for teachers as well as students. If the dominant standardized test no longer creates time pressure, there’s less need to use a ticking clock on classroom quizzes and exams. I don’t expect students to start looking forward to tests, but they should be less likely to dread them. That will give them a better chance at putting their best foot forward. It will also give them a more realistic preview of what it takes to excel in the future.

In school, timed tests teach kids that success is a sprint. But in life, success is a marathon. Wisdom is less about the speed of thought than the complexity of thinking. The students with the greatest potential aren’t always the ones who can rapidly spit out the right answers. They’re often the ones who take the time to ask the right questions.