Teaching LGBT history

Two days ago, "the California state senate passed a bill that would require public schools to add LGBT people and people with disabilities to the list of groups whose contributions to American society are recognized in social studies curricula.
The New York Times reports that,

… starting in the 2013-14 school year, [the bill] would prohibit districts and the California Board of Education from using textbooks or other instructional materials that reflect adversely on gay, bisexual and transgender Americans.
If the bill becomes law, California would be the first state to require the teaching of LGBT history."