I was asked to sing for the 8th grade graduation this year and...

for good is beyond cliched. do "Don't Have To Be So Sad" by Yo La Tengo.

Everyone and their mother's sister did For Good when the choral arrangement came out. My high school did it..as well as about 3 neighboring schools.

Our song my senior year was Always Look on the Bright Side of Life from Spamalot..but part of that was because we had all gone to see the show on broadway..and some Rascal Flatts song that I don't remember cause everybody hated it cause some sophomores picked it out....google says its Bless the Broken Road.
We also did Breakaway by Kelly Clarkson.

---

ughh...I had to sing For Good at my 8th grade graduation and 8th grade awards night 3 years ago.

All I can say is, DON'T SING FOR GOOD!
It will come back and haunt you for the rest of your life.

if your singing by yourself, and you have a pretty big vocal range, possibly Astonishing from Little Women might work...

"Go Gently Into the Morning"

I'm sure you were amazing.