A pep rally is the squad's job to run the room. The bleachers are full, the team being honored is down on the floor, and it falls to the cheerleaders to get a few hundred students clapping, stomping, and yelling on cue. The music has to do the heavy lifting because most of the crowd has never practiced a thing.
So the picks here are the ones everybody already knows: a stomp-clap anybody can follow, a chant that fills the gym, a chorus the whole student section shouts back without being told. Simple beats the squad can lead from the floor, and the rest of the building falls right in.
The list

Jump Around
House of Pain (clean)
⚡ Medium Energy“Best Moment
the "jump jump" squeal hook
Makes the gym bounce.

Sweet Caroline
Neil Diamond
⚡ High Energy“Best Moment
the "bah bah bah" horns
'Bum bum bum' singalong.

Don't Stop Believin'
Journey
⚡ High Energy“Best Moment
the "don't stop believin" line
Belief singalong.
“Best Moment
the "a little bit softer now"
'A little bit louder now' builder.
“Best Moment
that fiddle hoedown loop
Clap-along cue.
“Best Moment
the "young man" horn intro
Arms-up crowd dance.
“Best Moment
the "thunder" guitar tapping
Crowd 'Thunder!' chant.
“Best Moment
the "all aboard" laugh
Riff that rocks the gym.
“Best Moment
the stomp-stomp-clap
Stomp-stomp-clap unifier.

Our #1 pick
Seven Nation Army
The White Stripes
⚡ High Energy“Best Moment
the seven-note bass riff
Gym-wide stomp chant.
Make it theirs
The one rally chant that's truly yours is the one written around your school and your squad, with the team name right in the hook. That is the one we make.