When John Walton died in the crash of his experimental ultra light plane on Monday, the nation lost one of its foremost educational philanthropists and a leading advocate for school vouchers and tax credits.

A great friend to impoverished schoolchildren, Walton’s Children’s Scholarship Fund made scholarship grants to 70,000 children nationwide, 1,600 of them in New York. As an indication of the need the fund fills, it has received well over a million applications for scholarships that average $1,214. Walton and Wall Street buyout specialist Theodore Forstmann founded the fund in 1999 with a $50 million donation that Walton later increased.

“He was central in the nationwide effort to reform education,” said Peter Flanigan, a former Wall Street banker who founded Student Sponsor Partners of New York, “both through providing scholarships to needy kids and by organizing supporting funding, without ever taking the public lead.”

Legendarily taciturn, Walton was a doer, not a talker. He volunteered for combat duty in Vietnam and won the Silver Star. Never one to be tied to an office job, he made his living for several years as a crop duster. He founded a company to build trimaran sailboats. He skied the high country, and zipped along the roads near his relatively modest – for a multibillionaire – home in Jackson Hole, Wyo., on a homemade motorcycle. He also built the plane he crashed in, from a kit.

In his philanthropy, as well, Walton took risks. The fractious issue of school vouchers has kept more than a few business-minded humanitarians from promoting them.

He told USA Today last year that critics of vouchers ignore inner-city dropout rates. “They’re choosing the streets over a school that apparently doesn’t work for them,” Walton said. “If choice destroys the system, then why are we so sanguine about the choices those kids make?”

“Education is a $700-plus-billion-a-year industry,” Walton told Fortune magazine last year. “We aren’t trying to change public schools, we are trying to change the education environment so that public schools have to change for the better.”

The Children’s Scholarship Fund has large programs in Milwaukee, Philadelphia, Los Angeles, and 35 other cities nationwide. Responding to the recent closure of Catholic schools in New York, the CSF recently announced it was providing funds to an additional 3,200 students in the city’s Catholic dioceses.

Last year in a Fortune magazine profile, Walton was asked why he volunteered for combat duty. He was a medic attached to a Green Beret unit and won his Silver Star for evacuating the wounded under fire.

“I figured if you’re going to do something, you should do it the best you can,” Walton said.

He kept that policy going in his philanthropy and advocacy.

Mr. Forstmann, the CSF co-founder, said, “John didn’t just provide funding that allowed CSF to grow beyond our dreams, but he also devoted so much of his time and energy. He was a rock. America has suffered an incalculable loss with his passing.”