Go for it. I wore the same madras pants to my high school, colleage, and law school graduation.
Similarly, I wore a seersucker suit to middle school, hs, college and law school graduation. They make up for your coloring when you leave the party at 7am to get dressed for graduation.
You had a seersucker suit in middle school? You sir are a prep god.
Are you supposed to take off your jacket while wearing the gown and if so where do you put it? I'm also graduating in May and don't even remember what we did in high school.