Former Education Secretary Rod Paige told the Board: "History is what it is"
Tempers are flaring in Texas over controversial proposed changes to the US state's public school curriculum.
The changes, put forward by the Board of Education's conservative members, include referring to the slave trade as the "Atlantic triangular trade".
Critics say the changes are ideological and distort history, but proponents argue they are correcting a long-standing liberal bias in education.
The conservatives are expected to prevail in Friday's final vote.
The changes eliciting the most concern include diminishing the role Thomas Jefferson - principal author of the Declaration of Independence - in history courses because of his belief in the separation of church and state, and dropping references to a landmark court case that barred schools from segregating Mexican American students.
The amendments also cast the United Nations in a critical light, with students asked to evaluate whether the UN and its committees undermine US sovereignty - a common refrain for conservative Americans.
The new curriculum would emphasise the role of religion in America's founding, as well as promoting the superiority of the capitalist system.
The Board insists, though, that capitalism will only be referred to as "free enterprise system", largely because of the negative connotations of the word capitalism.
Criticism of 1950s McCarthyism, where suspected communists were aggressively questioned before government inquisitors, would also be toned down.
Texas is the second-largest consumer of textbooks in the country, after California.
Opponents of the changes worry that textbooks sold in other states will be written to comply with the new Texas standards, meaning that the alterations could impact curricula nationwide.
Rod Paige, who served as Secretary of Education under President George W Bush, urged the Board to delay its vote.
"We have allowed ideology to drive and define the standards of our Texas curriculum and it has swung from liberal to conservative depending on the members of state board," Mr Paige said during a day-long public hearing on Wednesday.
"What students are taught should not be the handmaiden of political ideology."
Over 200 witnesses registered to testify during the heated proceedings - a record for the Texas Board.