Getting students that wear regulation underwear to be naked will probably come later in the game. Much like removal of skirts, removal of regulation underwear during punishments might happen after a rule change and probably to increase the effectiveness of spankings or something. But that's not in the game yet.
i talked to him and the gym teacher after that i dont know what to do
She gives you the quest, you go talk to the guy, then IIRC, you go back to him and he gives them to you, then you go back and give them to her. Might have to wait a bit, can't remember if that was part of the quest, or just because it was only partially in the game when I did it...
Update!
No, this was a clean game, starting from the beginning.
Yeah, that's makes sense. I upgraded the rule section but forgot to set that definition for the intro. It should work from day two onwards.
Yes, it works fine from day 2 onwards.
The date where she talks about how the best murder mysteries are ones with lots of red herrings where the real killer remains a mystery until the end? That's got to be a foreshadowing of your investigation into the old headmaster, right? And that little taster of Arabella being spanked? The soon we get her enrolled in the school the better! And telling Rachal about wanting to implement a boner rule? Oh, I want to pass that rule right now! 
