Normally, we expect to get thanked when giving a few bucks to a good cause. When it comes to K-12 schooling, though, folks giving away millions have been slammed for their trouble.

Critics have accused the Bill & Melinda Gates Foundation and other deep-pocketed donors of trying to “buy” America’s schools. These critics exaggerate the influence of education philanthropy even as their overheated claims distract from the real issues posed by today’s savvy givers.

Education historian Diane Ravitch has attacked this “billionaire boys’ club,” declaring, “Bill Gates is using his vast resources to impose his will on the nation and to subvert the democratic process.” In the introduction to his recent book, “The Gift of Education,” DePaul University professor Kenneth Saltman writes: “The new philanthropy is at the forefront of a right-wing movement to corporatize education at multiple levels.”

These attacks have fueled much confusion, leading even more measured observers to wonder about the influence that these foundations are exerting on our public schools. In truth, even big-dollar philanthropy is pretty minuscule when viewed alongside our nation’s K-12 spending.

"In truth, even big-dollar philanthropy is pretty minuscule when viewed alongside our nation’s K-12 spending."--Frederick M. Hess

The five biggest K-12 givers in 2010 (the most recent year for which data are available) were the Gates Foundation ($209 million), the Walton Family Foundation ($110 million), the W.K. Kellogg Foundation ($58 million), the Michael and Susan Dell Foundation ($55 million) and the Silicon Valley Community Foundation ($35 million). The top 10 donors gave about $585 million in total, and the Foundation Center has reported total foundation giving that year of about $983 million to K-12 schooling. (Full disclosure: My own work is funded, in part, by foundations including Walton and Gates.)

This seems like a lot of money, but how significant is it really? Well, that $983 million amounts to less than one-sixth of 1 percent of the $650 billion that the U.S. spent on K-12 education in 2009-10. Indeed, all reported giving in 2010 was less than 5 percent of what New York City alone spent that year. Facebook founder Mark Zuckerberg gave an enormous, much-discussed gift of $100 million to the Newark, N.J., school system in 2010. His total gift, to be parceled out over five years, will amount to about 2 percent of that system’s spending during that time. As University of Arkansas professor Jay Greene wryly noted in 2005, we spend so much on public schools that even hundreds of millions given in philanthropy is like  tossing “buckets into the sea.”

That said, it is also true that “reform-minded” donors like the Gates and Walton foundations have figured out how to powerfully leverage their investments. For instance, $60 million in donor support (from the Walton, Broad, Robertson and Arnold foundations) proved critical in helping former Washington, D.C., Chancellor Michelle Rhee fund and win passage of a path-breaking collective bargaining agreement in 2010. Funders have also been critical in the burgeoning success of influential advocacy groups like Stand for Children, Advance Illinois, and ConnCAN. A wave of philanthropy has played a critical role in creating a charter-centric New Orleans school system that has posted impressive results and become a national model for charter advocates.

Whether one likes the reform agenda or not, it’s clear that Ravitch and her imitators are on to something when they observe that funders seem to be having an outsized impact. The reason for this is simple, and important.

Philanthropic dollars have an outsized influence because the vast majority of public funding is locked into salaries, benefits, bureaucracy and buildings. About 80 to 85 percent of school system dollars are steered into salaries and benefits alone. Paralyzed by regulations, contracts and a lack of imagination, superintendents find it hard to redeploy more than a tiny sliver of public funds.

Thus the success of education philanthropy is no conspiracy. And it’s not a consequence of huge dollars. Rather, it’s a case of relatively tiny, agile funders being able to move where muscle-bound state and district school systems, for all their billions, are stuck. Think Mighty Mouse, not Godzilla.

"It’s a case of relatively tiny, agile funders being able to move where muscle-bound state and district school systems...are stuck. Think Mighty Mouse, not Godzilla."--Frederick M. HessNow, such foundation giving is not unprecedented, but it is much more common today than it was a decade ago. And foundations investing more heavily in policy, big reforms and quasi-partnerships with the U.S. Department of Education pose new challenges.

There are legitimate concerns about the perils of groupthink: that foundations are close-mindedly wedded to pet reformers or consultants who tell them only what they want to hear, and that academics may be disinclined to challenge deep-pocketed funders.

So the skeptics do have a point. But here’s the irony: Their overblown attacks on the motives of philanthropists only ensure that their substantial concerns will get lost amid the invective. Meanwhile, the shrillness of these critics causes reformers to dig in even deeper. The sad upshot of this is a growing difficulty in having civil, informed debate about the wisdom of philanthropic efforts or reforms to teacher evaluation, charter schooling and the rest.

Those seeking to help remake American schooling should welcome tough-minded criticism. But a little gratitude — and a little less hysteria on the part of their critics — wouldn’t hurt, either.