Sondheim retired again in the 1980s and took the job he holds now as a senior adviser at the Greater Baltimore Committee, a business group that promotes the Baltimore region.
Retirement is a concept that scares Sondheim, but not as much as the concept of staying too long. "When you get to be my age people won't tell you you ought to retire and that worries me," Sondheim said.
Seven years ago, he wrote a letter to about a dozen of his closest friends asking that they let him know, through an anonymous letter if they must, when he should "hang up the spikes." None wrote back. He still worries that they're coddling the old man.
It is clear that they are not.
"I read that letter every month and I remind myself that first of all this is not the time [for him] to retire and I hope I would have that level of wisdom" to know when it was time for her to step down, said State Schools Superintendent Nancy S. Grasmick, who has known Sondheim for more than 40 years since she had a summer job in the office of Hochschild, Kohn.
Sondheim muses it might be time for another letter. He has been mentioning it to his old friends. This one might come with a self-addressed stamped envelope, maybe just a check-off box so the authors wouldn't have to worry that Sondheim could decipher their identities.
"We said, `Walter, you can do it, but we're throwing it in the trash,'" LeBow-Sachs said. "He's so afraid he's going to slip and people won't tell him. I would like to be that way when I'm 70, let alone 95."
Sondheim's last state school board meeting will be held Tuesday and Wednesday. He knows he leaves with unfinished business. The board must soon decide how - and whether - to link its new high school assessment tests to graduation. If the bar for graduation is set too high, there will be a flood of students who fail to earn their diplomas - and doubtless a flood of controversy. If the bar is set too low, the diplomas could be meaningless.
He worries that if it's done wrong, it could end up out of the hands of the school board - and into the hands of the Maryland Legislature. "In state after state where this has been done, a howl goes up," Sondheim said. "I would hate to have that happen here. I don't think we ought to rely on the legislature for that kind of education problem.
"I don't know the answer to this one," he said. "I don't envy them," he says of his soon-to-be former colleagues.
That kind of thoughtful discourse is what Marilyn D. Maultsby, the president of the school board, will miss.
"He's been the consummate statesman," she said. "I always refer to him as Mr. Accountability. He is steadfast in that."
"At my age," Sondheim says, "it's much easier to know the problems than know the solutions. The people younger than I am say they know the solutions.
"I hope they do, but I'm not so darn sure they do."