Though the annual "Messiah" performance at Rockefeller Memorial Chapel has been a tradition for more than a century, last Friday brought something new: Early Childhood and Lower School students from the Laboratory Schools were invited to sit in on the rehearsal. Students leaned in as trumpets rang out and the choir soared through the “Hallelujah Chorus,” many with mouths open and eyes wide as they took in the music and the space. Unlike the formal performance, where wiggles and giggles give way