The opinion can be found at the court's web site
http://www.ca9.uscourts.gov/ca9/newopinions.nsf/Opinions+by+date?OpenView&Start=1&Count=100&Expand=1.1 The case name is Fields v. Palmdale.
The Court's conclusion includes this statement:
We conclude only that the parents are possessed of no constitutional right to prevent the public schools from providing information on that subject to their students in any forum or manner they select.