If your school is ONLY state funded and doesn't have some sort of provision against established religion, go for it, but if you recieve federal money there shouldn't be a specific prayer said. Moment of silence works.
All of our highschools pray at graduation, it's tradition, it's culture, it's what we do. I don't think it'll change any time soon. Although, some nut job has already sued our school for the use of three crosses as a logo (it's been used for years, this moron recently moved here and decided to file a law suit). The VAST majority of this town A) wishes this man would shut up B) wishes this man would leave C) wishes this man would kick the bucket ... and I think opinion (A) is the minority of those three