Jose Espinoza-Morales, 7, learns about weather in Spanish during his second-grade talented and gifted dual language STEM class at Capitol Heights Elementary in Prince George’s County, Md. (Sarah L. Voisin/The Washington Post)

We have no idea how many gifted children are in the United States. We don’t know whether special handling of brilliant youths helps them. Spending a lot of tax dollars on such kids is not popular.

I learned this reading the best book on gifted education I have ever encountered, “Failing Our Brightest Kids: The Global Challenge of Educating High-Ability Students,” by Chester E. Finn Jr. and Brandon L. Wright. You would think, from the authors’ refreshingly honest description of how little we know about giftedness, that they would recommend we move on to programs with better data and more support, such as ensuring that every fourth-grader can read.

But Finn, a leading U.S. authority on schools for more than 30 years, and Wright, an up-and-coming education-policy expert, refuse to give up on the gifted. They identify promising developments in other countries and suggest improvements appealing even to people like me, who think most gifted classes in the United States are a waste of time.

What saves the book is its focus on bright low-income children. Too many of them lack the access to the top schools, enriched home life and challenging colleges where the most-effective gifted education occurs. Like me, the authors are impressed by Caroline Hoxby and Christopher Avery’s finding that just 34 percent of high-achieving students in the bottom quarter of family income attend any of the 238 most-selective colleges.

“These are young people, mind you, who succeeded in American K-12 education despite their families’ poverty, yet the system still failed to do right by them,” Finn and Wright say in the book.

So they troll for overlooked data in studies that seem to say gifted education doesn’t work. Researchers David Card and Laura Giuliano, for instance, say full-time classes for high-IQ students don’t raise their achievement, but they do help high-achievers, particularly low-income students whose IQs don’t meet the gifted standard. This may, the book says, indicate a problem with IQ as a measure of giftedness.

The authors find some nations that widen opportunity for the bright but disadvantaged. In South Korea, public boarding schools and magnet schools are more widespread than in the United States and offer more spaces to bright low-income students. Still, the authors conclude, most of the foreign countries that they studied do not “bend over backward to draw such children into their gifted education programs.”

Finn and Wright’s recommendations are the most interesting, if frustrating, part of the book. What they call their “arguably most important” advice is, “Let’s place this topic firmly on the policy agenda and rekindle the debate about how to have a society that prizes excellence as well as equity.” It’s a nice thought, but gifted education is distant from what Americans worry about these days. I have similar doubts about their call for more research on giftedness and more focus on top scorers in analyzing state test results. States are going in the opposite direction, trying to make mediocre results look good.

The authors do better with proposals that smart educators might be able to implement on their own. They suggest identifying potentially gifted students by marking the files of the top 5 percent of scorers in the standardized third-grade tests that nearly all states give and have teachers recommend another 5 percent.

They recommend changing schools’ emphases from fulfilling grade-by-grade requirements to mastering the material. If a fourth-grader is ready for sixth-grade work, give it to her. Bright students could accelerate their studies, something that many schools now discourage, and look for more outside school activities that are good for the gifted.

Will any of that work? Finn and Wright don’t make promises, but I think their ideas are worth a try, because what we are giving our brightest now, particularly those from impoverished families, leaves much to be desired.