It's Week 9 of the Iowa high school football season, so that means only one thing.

Time to re-learn about RPI!

RPI (ratings percentage index) has been used since 2018 by the IHSAA to determine playoff spots for Classes 5A, 4A and 3A . For Class 5A, it decides the entire field and seeding. For Classes 4A and 3A, it helps select four at-large bids.

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