My mother grew up in a tiny Canadian town north of Toronto, and hers was the only Jewish family for miles around. A visiting rabbi made sure the meat my grandmother put on the dinner table was kosher, and when the family slaughtered a cow she gave the best parts of the beef to her neighbors.

But all was not happy and serene. My mother told a story to me years ago, when I was a child, that still brings tears to my eyes. She was about to dig into a piece of chocolate cake at a town picnic when the father of a friend, seeing her with fork in hand, told her gleefully: "You can't eat that, it's made with pork lard. Ha, ha, ha."

Anti-Semitism to a little Jewish girl is never an abstraction, and an anecdote like this stings more than cold statistics. Mom always thought the story of the picnic and the chocolate cake was her mother's "aha!" moment. Not long afterward, the family decided to move on. My grandparents, after all, had left their native Poland to escape such prejudice.

They packed up and joined relatives in Washington, where Jews were beginning to flourish with their neighborhood delicatessens, bakeries and mom-and-pop grocery stores. Theirs was a hardscrabble life for a while, but they had found their American dream, and Mom told me shortly before she died, at the end of a long and happy life, that she never felt another anti-Semitic slight. (But for that thoughtless neighbor's cruel remark she might never have become an American citizen.)

I thought of Mom's story the other day when I read about Mona Dobrich, whose family moved to Georgetown, Del., 30 years ago. She grew up as the only Jew in her school. She eventually married, stayed in Georgetown and raised her daughter Samantha and her son Alex there, where they, too, were the only Jews in school. Samantha and Alex listened to Christian prayers at award ceremonies, potluck suppers and PTA meetings, she told The New York Times, and one day, like my grandmother, she had an "aha!" moment. A Christian minister told the Class of '04 that the only way to heavenly salvation was through faith in Jesus Christ. She saw the hurt in her children, and asked the Indian River School Board to consider more generic prayers for public occasions.

When her request became public, her neighbors organized protests that boiled over on to local talk radio. "What people here are saying is, 'Stop interfering with our traditions, stop interfering with our faith and leave our country the way we knew it to be,'" radio host Dan Gaffney told his listeners. Soon, what could have been settled amicably and with tolerance escalated into a lawsuit. Mrs. Dobrich, feeling threatened by angry telephone calls, sold the house and moved to nearby Wilmington. She sued the school board for damages. To paraphrase lyrics from "The Music Man": "You got trouble, big trouble, right here in the Indian River School District."

The Founding Fathers, most of whom were men of faith, bequeathed a government that separates church and state, protecting each of us in his or her faith (or in no faith at all). The minister at Samantha's graduation ceremony confused a commencement ceremony with a Sunday morning worship service. "Ultimately, [Jesus Christ] is the one I have to please," the Rev. Jerry Fike of Mount Olivet Brethren Church says. "If doing that places me at odds with the law of the land, I still have to follow Him."

Fair enough, but if Mr. Fike felt he could only preach a sermon at the commencement ceremony, the school board should have invited another minister whose convictions would enable him to preach the Gospel from his pulpit and deliver another message at a public-school commencement. Mr. Fike's insistence on doing it his way only divided the community. After a season of controversy galvanized the town against the Dobriches with protest meetings and angry letters to the editor of the local newspaper, one of Alex's classmates gave him a drawing of a pathway to heaven that excluded the "Jewboy."

Differences and misunderstandings become bigotry when an inflamed majority abuses the weak in its midst. Intolerance never lurks far beneath the surface, and snubs and slights can activate prejudice and intolerance, public and personal, and it becomes particularly insidious when a religious leader plays to the mob. Tolerance requires vigilance.

My mother was proud to become an American, in a place where she never again felt isolated for being Jewish. She often joked that in America she could have her chocolate cake and eat it, too. So should we all.