If you're not used to wear a suit, don't in any case ! You'll only feel very uncomfortable. I would choose a shirt, matching tie and NO jeans NO sneakers, nikes, reeboks,..... Dress casual but 'sharp' so that you show respect to whoever you will meet.
If the school is impossing uniforms on their students and staff, pay double attention to your appearance.
Greetz and good luck.
J.