We need to be clear on what IS and ISN'T being debated here. The Supreme Court has ruled on mandatory school prayer.
Abington Township School District v. Schempp (consolidated with Murray v. Curlett), 374 U.S. 203 (1963), United States Supreme Court case argued on February 27–28, 1963 and decided on June 17, 1963. In the case, the Court decided 8-1 in favor of the respondent, Edward Schempp, and declared school-sponsored Bible reading in public schools in the United States to be unconstitutional.
This was decided 46 years ago! Nearly a half of a century! Yet, you morons continue to want to claim this is being debated currently! No one to my knowledge, since 1963, has tried to argue that school prayer should be mandatory, or that it should be something done as a regular part of the school day. No one has argued that the schools should be able to write prayers, or that this should be left to the teacher's discretion. Those are red herrings you are tossing into the debate, because you can't argue the point being legitimately made.
IF an agent of the school voluntarily wants to lead a non-denominational prayer to students who voluntarily wish to pray, and it is not being done as part of the school's curricular activities (extracurricular), then it SHOULD be acceptable and fully constitutional to do so! You've not presented a case for why you can deny these people, under this specific scenario, the right guaranteed in the Constitution to religious exercise.