In a December 2007 lawsuit, [Advanced Placement European history student, Chad] Farnan, then a sophomore, accused Corbett of repeatedly promoting hostility toward Christians in class and advocating "irreligion over religion" in violation of the First Amendment's establishment clause.
The establishment clause prohibits the government from making any law "respecting an establishment of religion" and has been interpreted by U.S. courts to also prohibit government employees from displaying religious hostility. --Scott Martindale, The Orange County Register
So government employees are not allowed to talk about non-religious alternatives.
It gets worse.
Corbett made his "superstitious nonsense" remark during a class discussion about a 1993 court case in which former Capistrano Valley High science teacher John Peloza sued the Capistrano Unified School District, challenging its requirement that Peloza teach evolution. --Scott Martindale, The Orange County Register
So yes, this comment really was in the context of a conversation about evolution and creationism. I will admit that how the teacher said it is quite disrespectful, but to call it the "establishment of (ir)religion?!" Are teachers not allowed to express personal opinion? The court found the school district not liable for the teacher's comments, so clearly this was the teacher's opinion, so if it was just his opinion how does it constitute the government establishing, because that's what the first amendment is about, the government And if it's the government doing the establishing, why is it the teacher is the defendant, and not the government?
And the part that I fear the most: does this mean my telling my science students that creationism is "not a scientific statement" is also violating the freedom of speech and separation of Church and State? Should I wipe my lecture on the origins of life on Earth in the context of astrobiology in the fear that a student will charge me with something?
This is just ridiculous.