The 1987 US Supreme Court decision of Edwards v. Aguillard is important here. It "ruled that the teaching of creation science in science classes in public schools was unconstitutional and unaceptable". From that point "creation science" became "intelligent design" (which I believe was also ruled unconstitutional in a 2005 case, but I don't have the case before me). Those who favor the "creation science" approach are now using a clause in the Texas Department of Education guidelines for science books that reads the "strengths and weaknesses" of Darwin's theory should now be taught.
(Source: The Washington Spectator, January 1, 2008. "Is Darwin losing the battle with God?" by Lou Dubose).
