Why not do both?

You follow along behind Sarah, admiring the curve of her ass as it swings from side to side with every one of her steps. You enjoy the distraction for a while, before pulling out the Rulebook to make gym class a little more interesting.

"Old Rule: To conserve space in the school, male and female students will use the same changing room for gym class."

"Old Rule: The female gym uniform is limited to a slingshot leotard with a thong bottom. This does not relax the dress code rule forbidding bras."

You close the Rulebook and pack it away in your backpack. You walk into the locker room and it's a dream come true. The girls, long used to this changing arrangement, are completely casual about it, stripping down out of their skimpy, uniform skirts and tops to expose themselves to every boy in the room. It's enough to get your cock painfully hard as you watch them slipping into their scant leotards, cut to leave their tits entirely on display.

You turn back to look at Sarah who's changing at the locker next to yours. After years of fantasizing, you realize she's finally standing in front of you, totally naked, her perky C-cups pointed right at you as she ties her long, brown hair back in a ponytail. "So are you ready for the physical fitness exam today." You groan. You'd totally forgotten it was today, and the news is nearly enough to spoil your mood even though it was delivered by a gorgeous, topless woman.