Prayers are banned at football games because Catholics and Mormons sued the Baptists who were persecuting them in Santa Fe, Texas.
The whole ruling is because the various Christian denominations couldn't agree on who the real Christians were, and so were beating each other up on campus over whose prayer was better. Baptist kids were being sent to school with instructions to assault and belittle the kids of the other denominations, and the administrators were looking the other way. The Catholics and Mormons won the lawsuit, but the Baptists started vandalizing their homes and property and eventually ran then out of town.
http://en.wikipedia.org/wiki/Santa_Fe_Independent_School_Dist._v._Doe
- 86 47 -