The Texas State School Board passed a resolution on Friday asking textbook publishers to limit references to Islam in a 7 to 5 vote.
Social conservatives on the 15-member board warned of a creeping Muslim influence in the nation's educational publishing industry.
The one-page non-binding resolution cited world history books which the board claimed to have devoted more space to Islamic beliefs than Christian beliefs. The books are no longer used in Texas schools.
"Diverse reviewers have repeatedly documented gross pro-Islamic, anti-Christian distortions in social studies texts," read a preliminary draft of the resolution.
Board members said they want all religions to be covered equally and promised to reject submissions from publishers if their textbook favors one religion.
Kathy Miller, president of the Texas Freedom Network, which advocates for religious freedom, questioned the timing of the resolution. She pointed out that "anti-Muslim rhetoric in this country has reached fever pitch."
"This to me is a cosmetic procedure," she added. "And I think there are more important issues, like getting our textbooks paid for. This is an unnecessary distraction at this time."
Critics say the board's resolution discriminates against Islam.
"It's just more of the same Islamaphobic, xenophobic attitude we've been seeing around the country," said Mustafaa Carroll, executive director of the Council of American Islamic Relations of Texas.
"It's not like Muslims are not part of the country," he added. "This kind of attitude is not healthy - it's not even American."
Opponents of the resolution noted that social conservatives are not expected to control the board after the November 2 election.