One of the great mysteries of American schooling is gifted education. You hear about it occasionally, particularly in elementary schools, but what does it do?

I encountered not long ago a typically confusing gifted education situation. The parents of an elementary school student were told he had been designated gifted and was in his grade’s only gifted class, where he would get advanced instruction. But the teacher of that class said nothing about that during her back-to-school orientation for parents. The word got around that all classes at that school had gifted instruction. How it worked was not explained. The district website was similarly vague.

Americans appear to respect gifted programs. They are happy when their children qualify for them, usually by scoring high on special tests given in early grades. Gifted class instructors are supposed to give them deeper and more sophisticated lessons than they would receive in regular classes.

Gifted children are generally defined as those with exceptional talent or natural ability. Studies of programs designed to serve such students leave doubt about their effectiveness. One of the largest and most detailed just came out. It looked at 18,170 elementary school students who began kindergarten in 2010. You can find it by searching for “Do Students in Gifted Programs Perform Better?” Its results are not impressive.

Jason Grissom, public policy and education professor at Vanderbilt, and Christopher Redding, assistant education professor at the University of Florida, said in the study that “critically, we do not have rigorous national estimates of the relationship between receiving gifted services at the elementary level and student academic and nonacademic outcomes. In addition, little gifted research has linked the outcomes of gifted students with state-level gifted education policies.”

The two researchers searched their trove of data for the effect of gifted education on school absences and achievement of low-income and minority students, as well as the effect of state policies on gifted student participation and achievement. Participation in gifted programs showed little effect on absences. Black or impoverished students designated gifted did not have the gains in reading achievement that other gifted students had.

It did not seem to matter what approach states took to gifted education. States that defined giftedness made smaller learning gains than those that did not have a definition. States that monitored and provided funding for gifted programs saw smaller learning gains in mathematics than those without funding or monitoring.

Looking at past research, the authors said participation in gifted programs in single-school districts could have positive effects on achievement, but “whether such positive effects hold on average across programs is less clear.”

They said there was little evidence of varying outcomes in the many different gifted education approaches, such as pulling students out of regular classes for a few hours, having separate classes just for gifted students, providing enrichment activities outside of school, accelerating some subjects or grades, or having separate academies for the gifted. They said they suspect each approach has a different effect, but that was not something their study was able to uncover.

Johns Hopkins University psychologist Jonathan Plucker, president of the National Association for Gifted Children, made a similar point in a statement to me about the study: “This research is interesting and provides some directions for future studies, but it doesn’t tell us much about the effectiveness of advanced programs.”

The vagueness and confusion over what is going on in gifted programs raises the possibility that the varied approaches are not worth the time spent on them.

A few charter school networks, such as KIPP, IDEA and Uncommon, have achieved significant gains in achievement by accelerating instruction for all students. Those networks serve mostly Black, Hispanic and impoverished families. BASIS, a charter network serving mostly middle-class children, has a similar emphasis on acceleration. KIPP, IDEA, Uncommon and BASIS provide more learning time for students and more training and support for teachers than regular public schools do. The Grissom-Redding study did not look at charter schools.

Most gifted programs strive for enrichment, not acceleration. In elementary school, some students may skip grades, but gifted programs rarely seek that outcome. A few parents provide extra instruction and succeed in getting their children moved to higher grades.

My only experience with gifted education as a child was a program funded by the National Defense Education Act that allowed me and three other students at my high school to accelerate our math courses so we could take calculus at a local community college when we were 12th-graders. My children were not in gifted classes but were allowed to take college-level Advance Placement courses in high school.

I have discovered only two U.S. programs that provide extreme acceleration in math. One is at the University of Minnesota and the other in the Pasadena, Calif., public school district. Both programs have eighth-graders taking Advanced Placement Calculus BC, a course that admits less than 5 percent of high school seniors nationwide.

“Research on whether gifted programs improve student achievement is surprisingly inconclusive,” the Grissom and Redding study said. “As national evidence shows that the majority of elementary school gifted programs include four hours or less gifted educational services a week . . . the educational dose of gifted programs may be too slight to yield positive effects.”

Some researchers have suggested that school administrators support gifted education in part because it improves student retention and prevents loss of funds from families transferring to other schools to get gifted instruction. There appears to be little political support for extending gifted education to more students or making it more intensive. High schools are gradually encouraging more students to take AP and IB courses, but those efforts are usually not considered part of gifted education.

“We suspect that proponents of gifted education may well conclude that what our results suggest is that investment in gifted services needs to be increased, not decreased,” Grissom and Redding concluded. They said one way to reach that goal is with more and better research.

Gifted programs are apt to continue as long as enough parents embrace the notion of their children getting special instruction, even if the results are difficult to discern. It might be useful, however, to see if accelerated programs such as AP and IB provide a better alternative that would be available to all families who want it.