AUSTIN — The State Board of Education imposed tighter rules Friday on the citizen review panels that scrutinize proposed textbooks, potentially softening the ideological battles over science and religion that have long plagued the debate about what is taught in school.Tension over the issue has been building for years in the second-most-populous state, where the textbook market is so large that changes can affect the industry nationwide. Critics complain that a few activists with religious or ideological objections have too much power to shape what the state’s more than 5 million public school students learn. The 15-member education board has the final say on textbook content, but the review panels influence its decisions. Among the changes approved Friday is a mandate that teachers or professors be given priority for serving on the textbook panels for subjects in their areas of expertise. Election defeats have weakened the board’s bloc of social conservatives, who made headlines in recent years by pushing for de-emphasizing evolution in science books and requiring students to evaluate whether the United Nations undermined U.S. sovereignty. The review panels have also been dominated by social and religious conservatives who object to evolution and climate change entries in science textbooks. Also at Friday’s meeting, the board approved a new high school curriculum that drops algebra II as a graduation requirement for most students. Blocking conservative voices?Among the fierce conservatives still on the state board is David Bradley. He said that he did his best Friday to insert language mitigating what was approved but that “liberals are really trying to make it difficult for Christians and conservatives to have a voice in public education.” “Certainly there are some members that were unhappy with some of the experts that we’ve had in the past and certain reviewers,” he said. “Maybe it’s embarrassing when citizens step forth and show some of the blatant inaccuracies in our American history, references to our founding fathers, our Christian heritage, truly errors. But to try and silence them with intimidation, I think, is wrong and that’s what this is all about.” The catalyst for revamping the review panels came last summer, when two ardent evolution skeptics — a nutritionist and a chemical engineer — caused a tumultuous fight by challenging a proposed biology textbook that didn’t include information on creationism. “We don’t need laypeople making these highly specific and technical decisions on these books,” Thomas Ratliff, a Republican board member who pushed for Friday’s mandate, said during the board’s meeting in November. Ratliff said Friday that another proposed rule would allow the board, with a majority vote, to have panels of outside experts scrutinize any objections raised by the citizen panels — a further check on their power. Clashes still possibleThough modest, the changes approved Friday could have a major impact in Texas, where Republican Gov. Rick Perry bragged during his 2011 presidential campaign that students were taught both evolution and creationism. The previous year, the education board approved social studies curriculum in which children learned that the words separation of church and state were not in the Constitution and were asked to evaluate whether the United Nations undermines U.S. sovereignty. All the proposed changes deal only with textbook reviews and won’t stop larger clashes by education board members about textbooks. They also won’t affect panels that vet proposed curricula. One proposal requires all portions of proposed books to be reviewed by at least two panel members so that a single volunteer couldn’t raise objections. Other rules would let panelists submit majority and minority reports about proposed materials to the board and would restrict board members’ contact with reviewers so as not to unfairly influence them. A more ambitious plan that would have allowed the education board to remove panelists for inappropriate behavior failed Wednesday night on a 9-6 vote.Curriculum overhaulThe move to drop algebra II as a graduation requirement for most students grew from a measure passed overwhelmingly by the Legislature last year. That law also cut the number of standardized tests that high schoolers must pass from 15 to five. The board’s 14-1 vote Friday formally implements the new curriculum, which takes effect in September. It is designed to create greater course flexibility for students who want to focus on career training. Some policy experts say that Texas is watering down its graduation standards and that fewer students will take algebra II if they’re not required to. But industry leaders say the law will better prepare graduates for the modern workforce.