Im also applying to Andover and LŽville , you are supposed to feel comfortable, but dont forget that your clothing must show respect to the interviewer and the institution, this also doesnt mean you have to look like a banker:
IŽll quote what a former teacher from a Bs said about a thread like this:
"Deciding what to wear should fit in with your purpose in interviewing with the school. You are there to show them what you bring to the table, and to determine if the school fits what you are looking for. Sure, you should look groomed, but you should absolutely look like yourself. Wear an outfit that you can comfortably walk in, possibly over long stretches, and maybe not strictly on sidewalks. Wear something you can sit comfortably in without picking at your clothes, Occasionally at the boarding school where I teach, we see kids on tours dressed like mini bankers, and we feel so sorry for them. These are the kids who also tend to look terrified or unhappy, and are usually trying to project an image of something they are not. I would advise against dressing in a manner that erases all clues as to your personality"
HOPE YOU MAKE A GOOD CHOICE!! AND PLEASE TELL ME HOW IT GOES!!
BEST LUCK OF ALL!!