AUSTIN, Texas — Conservatives on the Texas State Board of Education were defiant Wednesday as a parade of critics came before them, most urging a fresh rewrite of new classroom social studies guidelines and a delay of a scheduled vote to adopt them.

Critics, including the president of the NAACP, a former U.S. education secretary and the committee that wrote the draft guidelines being edited by the board, complained that the proposal has become a vehicle for political ideology, has watered down the teaching of the civil rights movement and slavery and reveals a lack of historical knowledge from the board.

The standards will guide how history and social studies are taught to 4.8 million students over the next decade.

“Of course it’s political,” Republican David Bradley said to one critic who complained that the process was too focused on politics rather than history. “So what’s your solution? Would you support a benevolent dictator?”