This is up for debate and also many Christmas Trees, Menorahs and Creches are erected each year on public land.
Can you lead a prayer in public school?
Up until the 60s you could and it was done in the Founder's times as well. This is a recent atheistic occurrence.
The first amendment gives unlimited freedom - however the courts restricted it to beliefs, not practices
Can a child drink communion wine if that child is below the legal limit to drink alcohol? Yes because the child is expressing his beliefs.
I agree with you. The fact is our religious practices are being restricted more and more by ACLU and friends in courts. However when Islam is involved - they all act like the freedom of religious practices is unlimited.