Says it all, really. Congress may not legislate based on religion, if that's what you mean by freedom from religion. If you mean no preaching or religious symbols in public or no private religious schools. Charities run by religious institutions though, then no. Congress cannot legislate based on religion, but there is nothing saying it cannot legislate based on other factors.
"Religion cannot be taken away from people, it is their favorite toy and it will remain their favorite toy so as long as we are afraid of death. I am perfectly happy for these people to have these toys and to play with them at home and to hug themselves and share them to others who come by want to play with the toys. They are NOT to make me play with these toys, I will not play with these toys. Do not bring the toys to my house, do not make my children play with these toys. Don't say that my toys may not be allowed by their toys. Enough with religious bulling and religious intimidation. " - Christopher Hitchens
Freedom FROM religion would naturally be a choice given under freedom OF religion. Freedom of something means you have the freedom to make your own choices free of interference. Non-belief in religion is just as valid of a belief as any other and should be respected as such. This is why forced prayer in public schools or places of any type (christian or any type) is wrong per the 1st amendment. It is an infringement a persons personal freedom to choose and act according to their own beliefs.