With the opening notes of Edward Elgar’s traditional processional music Pomp and Circumstance, two long columns of graduates – the boys in purple robes and the girls in white – made their way down the aisle of the Tabernacle on Sunday afternoon. The audience rose as the music began and turned to face the students, cheering madly. This is the Martha’s Vineyard Regional High School’s Class of 2013, 184 graduates strong.