I'm Singing the Star Spangled Banner @ my School's Girl's Basketball Game tomorrow. Can I just have some encouragement and assurance please?

Kick ***, sweetheart. You got this.

Good luck. You'll be great.

Have you heard of self confidence? What about your relatives and friends encouraging you?

The song has a fairly high range, and it's easy to start too high to hit the high notes that occur later.  Before starting, sing "oh-o say" a couple of times, finding the lowest pitched "say" that's still clear.  Clear but not necessarily loud, since a microphone should be supplied.  Lean in for the quiet low notes, back away a little for the louder highs.

Are you seeking encouragement from the internet? I'm afraid you do not know how the internet works. Unless you are trying to kill yourself you will not get any sort of heart felt encouragement from here. In the mean time, have fun missing every single note tomorrow.