Any textbook is vastly different from any other textbook–even when the books are about the same topic. The books used in California are different than the books used in New York, which are different from the books use din Virginia. Each books tells the story of history with a different slant.

“Here is California, we try to find more progressive books,” Administrative Vice Principal Gary Gooch said. “A lot of the textbook publishers are more conservative so here, in this district, we try to find the really progressive, really cutting-edge publishers who are doing something new–something different from the more conservative publishers.”

In California high schools, it is up to each individual district what book to use, so long as it meets the state-approved standards and complies with the state-approved framework. For English and math, this means following common-core standard. For history, though, things are not as simple.

In 2016, a new framework of educational standards was passed by the state. This framework, which includes what facts student should know, and how to best teach that knowledge, has been met with considerable controversy.

“California’s history and social science curriculum framework is dangerously one-sided, biased and incomplete,” said Lance Izumi, past president of the California state Community College Board in a report. “Crucial facts such as the massive death toll of Communism in the twentieth century are omitted, while a left-leaning narrative is evident throughout.”

This left-leaning narrative is exemplified by factual errors that line up with the liberal perspective. According to the framework, the communists overthrew a horribly un-democratic, tsarist government in the Russian revolution, painting the communists as the (at least temporarily) “good guys.” In truth, many factions helped overthrow the Tsar in February of 1917; a democratic, moderate government then came to power. It was not until October of that year that the communists overthrew the democratic government and took power–certainly not the emancipators of suppressed, peasant Russia that they are painted as in the California framework.

But standard, and textbooks, tend not to every be perfectly middle-of-the-road. The Texas standards refuse to state slavery as the main cause of the Civil War and do not require textbooks or teachers to give instruction about the Ku Klux Klan or Jim Crow laws–an obvious example of glaring bias in the right-leaning direction.

A textbook is not the only–or even the most important–tool to a teach, though, and there are many other sources of bias–in both left and right directions.

“Often, textbook publishers, especially those big textbook publishers–think Houghton Mifflin, McGraw-Hill, Pearson–do try to sell to a wide market, so they fo try to be relatively agreeable to everyone,” Gooch said. “That is why we have teachers: to keep on top of the new and constantly changing progression…to keep a finger on [society’s] pulse and teach our students the more progressive, newer things that aren’t in textbooks.”