You want to dress as a Scot? Right then, for the event you describe The PC is out, the black barathea Argyll(silver buttons?) is out. Why? It is the most formal daywear attire we Scots have in our armoury. You would not wear a morning suit to school, I presume? So your best bet is your tweed waistcoat. Please,please,please leave the flat cap at home. You are after all dressing up as a Scot, not as an American wearing the kilt. Good luck and have fun!