This might be one of those "putting too much thought into some basic blue curtains" situations, but I've been thinking about it a lot. Enjoy the following sleep-deprived ramble (and continuing ramble in the tags)

I feel like the line "and if I finally break the rules, I will know of my world, I'm the ruler" means so much. We only ever hear it twice ("cool as I think I am," and "dirty dudes must die"), even though the first part ("If I can finally be cool I will know that I'm not a loser") is played numerous times, and has a LOT of importance placed on it. Dirty Dudes is obvious by explaining how Grace is falling to what she would consider satanism in the name of God, but I personally see the first usage as kind of meta. Peter is singing the song about him and Stephanie, right? Well, in the other two Hatchetfield musicals, there are both couples that slowly fall in love over the course of the runtime. And you know what? They all die at the end. Hatchetfield dies at the end. It's because the Lords didn't know the main characters personally, or else weren't asked, and they were on the bad guy's side.

The Lords in Black are very much the bad guys. They feed from people's wants and their desperation to reach fulfillment (filling the holes), and actively cause destruction to cause more want and desperation. So "breaking the rules" by making them join the good guys side, just for once, causes the nerds to be known and protected so long as they pay the price. And they do. And that's why Nerdy Prudes has a good-ish ending. The second final song "The Best of You," as weird as it is, is entirely focused on Pete and Steph, who broke the rules by not dying, and became the "Rulers," homecoming king and queen, as a result (I know it wasn't explicitly stated they were king and queen but it wasn't a plot point at all so let me pretend lol).

So basically if Grace Chastity weren't there, they would have failed and Hatchetfield would have died again.

EDIT while listening to the music again I found another half-sung form of the lyric in "cool as I think I am (reprise)" that mashes the two verses together ("If I can finally break the rules, I will know that you have to do it"). This still goes with my thought process though since it's literally during the point where the normal rules of the couple dying are broken. They are literally breaking the rule where they had to sacrifice themselves. Thanks Max thanks Grace you saved the world from a disaster you caused <3