The official policy if you order from the Mac online store is that you must show proof that you are enrolled (not just accepted) in a college program.
My experience: when I went to my local store in person, and asked for a student discount for my High School student, the only question was, "what High School". Then they gave me the student discount. Of course, your mileage may vary.
Do not neglect the purchase of (newly available) AppleCare+, so that your new MacBook will be covered for both warranty issues for three years, and broken screen (with a more modest co-payment) for that time as well. You have only 60 days to buy it, or it is dead to you.