It is forbidden because the justices failed to see and honor orig. intent of the founders.
Here's where we would end up if prayer was allowed in public schools:
Monday: Islamic prayer. (Sunni on odd numbered Mondays; Shiite on even numbered Mondays.)
Tuesday: Christian: (Protestant on odd numbered Tuesdays; Catholic on even numbered Tuesdays.)
Wednesday: Buddhist prayer
Thursday: Hindu prayer
Friday: Atheist prayer to the Giant Spaghetti Monster.