Need help finding a zombie story (teens/young adult novel)!

Hi everyone! I’ve been searching for this novel about a zombie apocalypse for years now. It was an INCREDIBLE and spooky story (and I’m someone that hates zombies). Please help me find the name of this book!

Details:

- I read this around 2015-2018

- this book was either for teens or 9-12s, not an adult novel

Plot:

It’s set in a school (middle or high school?) and follows multiple POVs. The main character I think is a student. They get stuck in different parts of the school during the apocalypse and have to survive as the school is slowly infiltrated.

The MAIN THING I REMEMBER is that on the first page of each chapter, there was an illustration of silhouette zombie hoards approaching from the page corner. With each chapter, the hoard got bigger and closer (meant to show that the school was getting more and more overrun and they needed to escape).

The cover was probably a lot of red and black.

Thanks for your help! Please help me find this amazing book as I don’t remember the ending 🥹