I like field trips so much that my boys go not just on their regular school-organized trips but also on Hood Academy field trips of my own design.

Over the years, we’ve visited the State Capitol and state museums of natural science and history in Raleigh, the Moore’s Creek National Battlefield near Wilmington, the U.S.S. North Carolina in Wilmington, Tryon Palace in New Bern, the Alamance Battleground historic site near Burlington, the House in the Horseshoe historic site near Sanford, the Reed Gold Mine near Midland, and most of the Smithsonian Institution sites and monuments in Washington, D.C., among others.

Admittedly, my enthusiasm for Hood Academy trips may not be widely shared among my students. My expectation, however, is that as the boys grow into young men, they will appreciate having been exposed to real places, artifacts, and experiences outside the printed page or flickering screen.

Until now, my expectation was based primarily on personal experience. There has been little empirical study of the educational benefits of field trips. Although there is a widespread assumption they are valuable, experimental evidence is hard to come by — a deficiency present in many other areas of education policy, by the way.

The best way to test the effects of a particular intervention is a randomized trial in which an experimental group receives the intervention and an otherwise comparable control group doesn’t. But large-scale randomized trials are expensive and hard to pull off. If the study lasts several years, there can be a great deal of attrition, reducing the sample size and thus the likelihood of obtaining statistically significant results — especially if the attrition isn’t equally distributed between the experimental and control groups.

Without randomized trials, you can’t be sure that the apparent benefits of an intervention are really valid. Consider two schools that seem comparable in many respects. They are of a similar size, composition, and financial status. School A often sends its kids to field trips. School B doesn’t. To discover that School A has better outcomes is not necessarily to establish that the field trips had anything to do with it. For example, perhaps schools with good leaders and active parents are more likely both to schedule field trips and to do other things that improve student attitudes and learning.

That’s why a recent study by the University of Arkansas’s Jay Greene, Brian Kisida, and Daniel Bowen is so interesting. The trio of researchers seized a unique opportunity to conduct a randomized trial. In 2011, the Crystal Bridges Museum of American Art opened its doors in northwest Arkansas. It is the first major art museum to have opened in the United States in the past four decades, and offers a swath of Arkansas school systems close proximity to such a facility for the first time. It also uses endowment funds to underwrite the cost of school field trips to the museum, including free admission, lunch, and reimbursements both for the bus trip and for substitute teachers back home to replace those on the trip.

Because more schools wanted to conduct field trips to the museum than could immediately be accommodated, the museum used a lottery to assign spots for tours. That meant that the population of schools making the field trip and the population of schools not making the field trip were about as comparable as possible.

So, did participation make any difference? The researchers used surveys and a test of critical thinking skills to evaluate the effects. “Students randomly assigned to receive a school tour of an art museum experience improvements in their knowledge of and ability to think critically about art, display stronger historical empathy, develop higher tolerance, and are more likely to visit such cultural institutions as art museums in the future,” the researchers concluded. The benefits were strongest for disadvantaged students, who are less likely to visit cultural institutions on their own.

And now, back to planning Hood Academy’s field-trip itinerary for 2014.

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Hood is president of the John Locke Foundation.