Here’s my problem: My admission counselor has just sent me an email of my interview schedule this Saturday morning. The thing is, I have a VERY VERY important work that day and I can’t attend that Interview. Will telling him that I am busy at that time and re-scheduling my interview create a negative impression?? I’m too afraid to tell him 
My guess is this: if you explain why you cannot attend, he or she will be impressed by your dedication to work. All of us have had to reschedule. You are giving plenty of advance notice. It’s hard to see how this would be a problem.
Not emailing him back and just leaving him hanging would leave a worse impression. As long as you have a legitimate reason, he should be fine with rescheduling. Email him, apologize for an possible inconvenience you may cause him, mention how much you love the school and want to interview, and ask to reschedule. I had two interviewers try to set up interviews with me at times when I would be out of the country. I emailed them and asked to reschedule and had no problems.
You’re not one of those students who are afraid of interviews, are you?
It is very normal to have to reschedule, nothing to be nervous about. Please be open and forthcoming in your dealings for smoothest outcomes. Do not hide or avoid or delay in your dealings. No one can fault you for truth and honesty.
@JustOneDad: No not really, actually I myself request for the interview since I think It would increase my chance of getting in.
OK. I’ve seen enough posts to know you have to ask. The other thing I have to ask, as a parent, of course 
is what is “VERY VERY important work”?
They know that you are a busy high school student with lots of extracurricular activities or jobs after school hours. I tutor after school for couple of hours, so I mostly have to reschedule all of the interview requests to a later hour. Don’t worry.
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Re #7: What would you like to wager that most of adults who conduct these interviews believe – with considerable justification – that their schedules are even more constrained than the typical seventeen-year-old applicant’s?
TT, if the adults have busy schedules, they should well be able to understand the need for anyone to reschedule an interview. I don’t think the age of a person enters into it.
RE #8
Your point being?
At the end of the day, both the student AND the interviewer have to find the optimal time to meet among their busy schedules.
@MidwestDad3 and @viphan: Of course, what is extremely – and obviously – germane is the “busy” interviewer has the prerogative to submit a truly negative report, whereas the “busy” teenager can do NOTHING to harm the interviewer. I truly have never known (or even heard) of an interviewer that would do so, but we live in the “real world.” Why incur the risk?
You’re correct @TopTier but I think the risk is lessened a bit here because the communication actually came from the admissions counselor, and not the interviewer. I don’t think much harm could come from explaining the situation to the AC, and asking if a different slot could be arranged. IMO, it shows that the student takes his work obligations seriously.