A Muslim advocacy group has succeeded, for the past five years, in promoting a school textbook containing the bizarre claim that Muslim explorers preceded Christopher Columbus to North America and became Algonquin chiefs: Textbook on Arabs removes blunder.

Peter DiGangi, director of Canada’s Algonquin Nation Secretariat in Quebec, called claims in the book, the “Arab World Studies Notebook,” “preposterous” and “outlandish,” saying nothing in the tribe’s written or oral history support them.

The 540-page book says the Muslim explorers married into the Algonquin tribe, resulting in 17th-century tribal chiefs named Abdul-Rahim and Abdallah Ibn Malik.

Mr. DiGangi said the guide’s author and editor, Audrey Shabbas, and the Middle East Policy Council (MEPC), a Washington advocacy group that promoted the curriculum to school districts in 155 U.S. cities, have been unresponsive to his concerns since November.

But Ms. Shabbas said this week the passage was removed immediately from subsequent copies, and that she was “giving careful and thoughtful attention” on how to notify the 1,200 teachers who have been given copies of the book in the past five years.

This claim to Muslim precedence in North America has also been spread in the United States:

Meanwhile, the Thomas B. Fordham Foundation this week issued a report that is critical of “Arab World Studies Notebook.”

The study, titled “The Stealth Curriculum: Manipulating America’s History Teachers,” reviewed many curriculum supplements and “professional development” programs aimed at schoolteachers.

“It appeared that the creation and dissemination of these materials, often through professional development institutes and [teacher] in-service programs, had fallen into the eager hands of interest groups and ideologues yearning to use America’s public school classrooms to shape the minds of tomorrow’s citizens by manipulating what today’s teachers are introducing into the lessons of today’s children,” the Fordham study concluded.

Mr. Roth said the “Arab World Studies Notebook” is the primary reference text used in the council’s program of teacher workshops conducted by Ms. Shabbas, which have numbered more than 268 in 155 cities since 1987.

The book, offered at a markdown of $15 from $49.95, has 90 readings and lesson plans covering the history and culture of the Arab world, the broader Middle East and Islam worldwide. “A lot of teachers use it,” Mr. Roth said.

UPDATE: Here is the actual workbook, still available online: Arab World Studies Notebook - Muslim Explorers.