AUSTIN, Tex.  In an evenly split vote, the State Board of Education on Thursday upheld teaching evolution as accepted mainstream science.

But social conservatives on the board, using a series of amendments tailored to particular school subjects, succeeded in requiring teachers to evaluate critically a variety of scientific principles like cell formation and the Big Bang.

The debate over new curriculum requirements, to take effect in 2010, stands to influence educational standards nationwide. Once every decade, major textbook publishers revise their offerings to match the requirements newly set forth by Texas, which is one of their largest bulk customers.

More than 80 years after the biology teacher John Scopes was tried on charges of illegally teaching evolution in Tennessee, the controversy here has played out with more subtlety, involving political code words and efforts to undermine the theory itself.