This whole bit of "slotting" is rather unfortunate. Judges need to stick strictly to their grading rubric. I also wonder if it could be advantageous to have school names "blocked" from the judges so that all they see is "Band #1", "Band #2". You'd also have to have a way to keep the judges from hearing the announcer calling out which band is now performing. This way you could partially rule out the possibility of judges having it in their mind that, "Oh this is a band that deserves to move on, they may have messed up a little in preliminaries, but based on who they are, they should move on."