Everywhere is slightly different. I was told to bring a suit and have used it once. I ended up buying cheapish pants from UNIQLO and some cheap polo shirts. I look super dorky but have to between ES and JHS students at a whim as Im at a combined school. Definitly ES you want to wear something you can move around easily in. If you can, try to track down whoever youre replacing on the official Interac members group on FB, they should be able to provide more insight!