Political debate once studied in school textbooks has now moved off the pages and into the boardrooms where textbook content is currently being decided.

The latest debate is happening in Texas, where the state board of education is scheduled to hold public hearings Wednesday on which social studies books to approve for use in elementary schools.

While board members don't anticipate much controversy over the choice of books being considered, they do expect that "outside groups" will try to affect the book selections, a trend that has been developing over the years.

"Texas has a lot of conservative people; years ago, they became upset and thought there was liberal bias in books," said Texas Board of Education Chairwoman Grace Shore. "It also has diversity, with a large Hispanic and black population. People are interested in seeing that those groups are portrayed accurately."

Texas wouldn't be the first place where special interest groups have tried to influence the school curricula. Across the country, 21 states — called "adoption states" — have a review process in which public input is received before the state approves and funds reading material for local school districts and teachers.

What gets approved in three of those adoption states — Texas, California and Florida — could have a massive impact on what the rest of the nation's schoolchildren read.

"Those three states have a very significant impact on textbook publishing. What happens in those volumes wind up being at least the basis of national editions sold throughout the country," said Stephen Driesler, executive director of the Association of American Publishers school division.

As Driesler explained, that's because Texas and California alone account for almost $1.5 billion of the $4.5 billion in textbook publishing revenues. As the largest share of the market, publishers and authors produce books that aim to please those states.

So it's to those states that influence peddlers head when they are seeking to have their issues included in the curriculum.

Some textbooks already demonstrate such successes. In California, for example, health food activists convinced California lawmakers to outlaw mention of "foods of low nutritive value" in its schoolbooks.

That means the short story previously called "A Perfect Day for Ice Cream" is now called "A Perfect Day." The reference to an ice-cream shop excursion has been edited out, and math word problems have been revised so that items like lollipops and candy bars are not included to teach kids arithmetic.

In Texas, the science book Environmental Science: Creating a Sustainable Future, was tossed out in part because it was deemed biased toward the environmentalist perspective.

"It said that the root cause of environmental problems was that too many people own land and the government can’t control them," said Shore. "It said that the settlers hated the forests and burned them down to grow food, while the Indians lived in harmony with the forest. That was not our curriculum."

The text also gave quite a bit of play to the problem of global warming in a way that some groups saw as anti-industry.

Such degrees of influence have some observers cautioning that censorship could be on the horizon.

"It’s really hard to define censorship because there are just so many days in the school year and so many pages in a book," said Joan DelFattore, an expert on First Amendment issues in education at the University of Delaware and author of What Johnny Shouldn't Read. "Somebody has to make a decision as to what goes in and what stays out."

But, DelFattore added, "What I find particularly troubling is efforts people make to exclude completely any viewpoints with which they disagree."

Shore said that balance is the key to writing an effective and objective textbook.

"No book is written in a vacuum," Shore said. "The authors have an agenda in mind. You don’t have a book entirely devoid of a viewpoint. It’s a matter of making sure there’s a balance."

While personal viewpoints will always have a major impact on the approval of certain books, Driesler said that doesn't mean other perspectives can be thrown to the wind.

"The system works best when the local schools and teachers are given a choice," Driesler said. "To deny the opportunity for philosophical or political reasons is unfair to publishers and ultimately to the kids and teachers who have their choices limited."