"The U.S. Supreme Court banned school-sponsored prayer in public schools in a 1962 decision, saying that it violated the First Amendment. But students are allowed to meet and pray on school grounds as long as they do it privately and don't try to force others to do the same." /1
If you want teachers or administration to LEAD prayers, you have two options. Parochial schools (Catholic, Lutheran, etc.) may lead prayers. Or, teachers/administrators must lead prayers in EVERY religious tradition present among students, and allow anyone to opt-out. /3