And you can buy yourself some time. Is it a MS or a HS? If it's MS and you have a fall concert, wear the band t-shirt. If they don't have one, that's easy to institute. For the Winter concert go Ugly Christmas sweaters or Christmas colors with Black from the waist down and Festive colors from the waist up. Only big rule I would have is that anyone wearing a skirt/dress needs to be past the knee when they sit down.

See how things go. You can always make adjustments for the Spring based on that info but don't add extra just because. Year one will be exciting enough and as others said, it might not even be broken.