Four years ago, I stumbled across startling research that remedial courses in community colleges — a backbone of American higher education — often do no good, and that colleges do not adequately inform students about the true consequences of the placement tests that put students in those remedial courses.

Researchers Katherine L. Hughes and Judith Scott-Clayton in their 2011 paper said 92 percent of two-year colleges used placement test scores to decide if students would be consigned to remedial courses that they had to pay for, but for which they earned no credit. The College Board’s popular ACCUPLACER placement test failed to mention this critical issue, instead obscuring it with happy talk.

“You cannot ‘pass’ or ‘fail’ the placement tests, but it is very important that you do your very best on these tests so that you have an accurate measure of your academic skills,” a College Board guide said.

Huh? As Hughes and Scott-Clayton pointed out, the tests were used not just to measure skills but “as a high-stakes determinant of students’ access to college-level courses.”

I asked College Board officials to defend their guide. They appeared to be afraid of hurting students’ self-esteem.

“We believe that students who will require remediation but have the desire to obtain a college degree deserve encouragement,” a College Board spokeswoman told me. “To inform students that they are failures as they are seeking to redefine themselves or get insight into their own college potential would be counterproductive.”

The College Board has since removed the deceptive language, but the exams are still handed out at many community colleges with little warning of their importance. Critics have noted that if the applicants knew how much rode on their scores they might spend some time preparing for the tests. Many of these students are recent high school graduates who haven’t looked at a book all summer. Others have been out of school for years.

A richly detailed new book on strategies for community college improvement — “Redesigning America’s Community Colleges” — argues that the admissions system should get students into for-credit courses as soon as possible. Instead, the book says, the system “has an opposite purpose: to identify some group of students who will be kept out of a college-level program of study, or whose entry will at least be delayed.”

More than half of entering students at community colleges are required to take remedial courses in at least one subject in order to be eligible for for-credit courses. Many administrators and professors appear to believe in the system, but recent research shows that placement tests do a poor job of determining who needs help and what kind of help they need.

There are useful alternatives, if colleges can be persuaded to experiment.

Some California community colleges have enjoyed positive results from giving their placement tests to high school juniors, so they can see if they would qualify for for-credit courses and have time, if they fall short, to get ready for those tests before they apply to college. Montgomery College and the University of the District of Columbia have similar programs.

Some colleges, including Montgomery, have experimented with giving more weight to high school grades when deciding who needs remediation, an approach Chester E. Finn Jr. of the Fordham Institute has denounced as threatening the whole notion of college readiness. (Maryland Gov. Larry Hogan just named Finn to one of two open seats on the state’s Board of Education.)

The cost of remedial instruction in community colleges is estimated at $4 billion a year. The tests are so woven into the admissions system that it will be difficult to uproot them. But researchers on community colleges say the system has to move away from wasting students’ time and money in courses that don’t work and find ways to support them as they tackle for-credit courses.

That will require wholesale changes in professors’ attitudes, access to advisers and the basic structure of community college courses and programs, all topics for future columns.