tonight I am singing infront of my school, and i'm beyond scared. In the past hour i've had multiple people tell me i'm not good/i'm gonna get wrecked/i cant do it, and im really nervous, help?

Dont lusten to blies.  Good grief.  What morons go to your school??  I expect they are trying to throw you off your game because they know they arent going to do well.    Nastiness like that is always about the bully and their feelings of inadequacy.  They bully to feel better about themselves.  If youve practiced as you should then you know youll do well and thats all that matters