Religion is a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects. http://dictionary.reference.com/browse/religion
And the courts have ruled atheism is a religion:
Check it out:
A White House petition to ban the teaching of creationism and Intelligent Design in American classrooms has garnered 23,715 signatures in one week.
“Both of these so-called ‘theories’ have no basis in scientific fact, and have absolutely zero evidence pointing towards these conjectures. These types of loopholes in our education are partially to blame for our dangerously low student performances in math and science,” reads the petition created by someone listed as A.J. of Vienna, Virginia. “Therefore, we petition the Obama Administration to ban the teachings of these conjectures that contradict Evolution.”
The petition must receive 100,000 signatures by July 15 to guaranteed a response by the Obama Administration.Continue reading on www.breitbart.com