^^I thought the exact same thing and I haven't really performed outside my school so far because well, at school you have people close to you and they'll stand up for you...
It's just a chance you'll have to take I guess but it's best to wait a little until you are confident enough. I wasn't exactly convinced I'd do well but I just went for it 'cause someone told me you should seize every opportunity so that's exactly what I did.
Just build it up...perform for small group of friends, then for more people...and so on...
(thanks for the compliment btw

)
DQ