Well, if it's a requirement then it is important. At least so you get accepted. It may vary though from school to school, ask a teacher from that particular one, or a student, I don't know.I don't think they'll give you hard pieces though, you can practice with short little pieces. Just take it easy and get a good quick glimpse of the whole piece before playing it.By next Saturday do you mean tomorrow or the 19th?
The 19th.
Oh ok, for a second I thought it was tomorrow . Dedicate part of your practice time just to sight reading, not much, 15 min is more than enough I think, do it sporadically during the day, sight read for 5 min as a warm up, before you start practicing your repertoire. Pick random pieces in IMSLP. Try sight reading hard pieces too so that when the time comes, the ones from the audition look easier.
Edit: It can also be like, if your pieces aren't the best, but your sight reading is freaking amazing, it might save you. Also the other way around: If your pieces are really well played, they wont care if your sight reading isn't.
So I have this audition next Saturday, and apparently I have to do some sight reading. I freaking SUCK at sight reading!!!
haven't you asked this question before?