There is a critical difference between private individual speech and speech promoted by the government. But once the state decides to help broadcast one person's speech to everyone in the park because it is popular, that address becomes state-sponsored speech. Public schools must be neutral on religion to protect the rights of everyone. Students should not be pressured to pray. Our First Amendment rights are not open to a popularity contest.
Prayer is a deeply personal experience, best left to individuals, their families, and conscience.
It is not the government's job to encourage prayer. School officials and student majorities should never be allowed to bully other children into religious worship. The Bill of Rights provides for individual freedom of conscience, not a tyranny of the majority. In any community, there are diverse religious communities, with different religious traditions and people who have chosen no spiritual path at all. No prayer would please everyone.