Body language matters more than you think. You applied for a good school. You had written the perfect self-introduction, sent it directly to the school and finally you got an interview. You prepared well for both information about the school and the interviewers, practising a lot on interview questions and answers. During your interview, things went well. You answered all the questions perfectly. However, the last word you heard from your interviewer was "goodbye" as you left the room.
What went wrong? Maybe you have got your body language for the interview wrong. Less than 10% of what we really communicate comes from the way of spoken communication, with the rest coming from how we say it, how we speak, how we sit and what we look like. Slouch (无精打采) in your chaff and you look bored and uninterested. Cross your arms and you look unfriendly. Sitting up Straight means that you are interested and listening.
If you want to succeed in your school interview, get your body language right and make sure what you say sounds polite. Interviewers care about not only what you say but also how you say it in a right way.