NEW YORK (TheStreet) -- If public schools were the only option for U.S. students, parents would make sure they provided the best education available, says Berkshire Hathaway (BRK.A) - Get Report CEO Warren Buffett. Instead, their performance has lagged because the richest and most powerful families don't use them.

"The wealthy in many cities have opted out of public schools," Buffett said in a panel discussion on CNBC's "Squawk Box" on Monday, where he was joined by Berkshire Hathaway Vice Chairman Charlie Munger and former Microsoft (MSFT) - Get Report CEO Bill Gates. Well-off families "may engage in philanthropy, but their own kids, they send them to private schools."

During a lengthy interview broadcast from Omaha, Neb., where Berkshire Hathaway held its annual shareholders meeting over the weekend, the three also touched on global and national issues from oil prices to interest rates, health care and criticism of fast-food chain McDonald's (MCD) - Get Report.

"It's the elite academic types in America who say it's the wrong kind of food, the wrong kind of things, the jobs don't pay very much," said the 91-year-old Munger. In fact, he said, "it's one of the most successful educational institutions in the U.S. They take people and give them a first job, which helps them get a second job. They do a very, very good job of taking troubled youth and making model citizens."

Teens who take entry-level jobs at McDonald's, including one in Buffett's neighborhood that the billionaire frequently visits, are learning job skills from arriving on time to counting money and being polite to customers, he said. "The people know me by name," he said.

McDonald's is among U.S. companies criticized by employees who say it doesn't pay a living wage for entry-level jobs. It's a complaint voiced by many workers holding the lowest-level positions at U.S. companies, some of whom have backed raising the country's minimum wage.

Such a move wouldn't make things better, the three men argued. As a mechanism to increase wealth, the earned-income tax credit holds more promise, said Gates, a philanthropist who's among the world's richest people.

"People who want huge, high minimum-wage increases will hurt the people they're trying to help," Munger said. "It's massively stupid. You ought to be very cautious of raising the minimum wage."

Munger also had harsh words for what he described as a bloated health care system that exploits an aging population.

"I would come down hard, if I had any power in the system, against prolonging [life] so you can bill the government more and more," he said. "You're lining your own pockets in a perfectly disgusting way. The health care system has a lot to atone for. If you actually go in the hospitals, you'll find people just lying there, huge invoices going out and no possibility they're ever improving."

Politically, Buffett said he remains an avid supporter of Hillary Clinton, despite questions about the destruction of emails from her tenure as Secretary of State and donations to the family foundation.

"I know the full range of things that can be said negatively about Hillary, but I'm 100% for her," he said. " I don't know anything that's worse about her than about me."