I actually really love this idea.
Writing the beginning and the ending first feels like giving the story direction instead of just hoping it finds its way. And yeah, that “pointless middle” part is way too real

I might try this for my next project.
if you like that? You'll love this... here's the secret to "pace"...
lets assume you decided 200 (ish) pages, standard first paperback.
that's 80k words, lets say 100k words, upper limit. Allow for what-not.
100k / 5k = 20 chapters.
Chappie # Chappie Goal
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1. girl sits behind boy in a class. Thinking, daydreaming, dreaming, the works.
2. girls friends go with her, to spy on boy in gym. check out the goods. Looks hot.
3. best friend, bad news. He's a geek among geeks in the math and comp sci department.
4. all her friends and her circle, work on her over this. That Ick, ewww.
5. she catches hell trying to stick up for boy, but its no use.
(OP gets the idea)
18. Girl rocks boys world silly, for 5K words, he deserves it.
(19 and 20, if you *earned* it... are for aftermath, etc. Happy ever after, or, set up next book's slop(I mean... "premise")
You can start to write, with this.
as you get ideas? chapters will get numbered and put in.
I think chappie 6 or 7 is TWIST,
she finds out gossip he's *secretly* a raging tough guy, hides it, because computer department.
write those patented "girl whining in her head, about boy" as they come to you, you can number them and slap them in later.
You can see how this goes now.
seat of the pants for each chapter, baby. Room to breathe, be original. No straight-jacket.
Just accomplish that chapter's goal.
its okay to change your outline for whatever reason as you're in the heat of battle :
---My character wouldn't do that !!! (she's only half that trashy)
---Plot hole needs plugged, more desperately than this feMC's hole needs plugged
---This chapter too whiny.
---This chapter not whiny enough.
Whoa, pulled of a MAJOR smut chappie, Let's see where this puppy gets shoved in at...