Riku didn't expect Sora to choose the second option. It had pretty much just been thrown in there as a mental finger to this school and his high school experience in general.
So when Sora actually picked that one, Riku just blinked at him a few times as he tried to process it.
Then he broke out into a big grin. "Okay. Follow me."
He chose the room for his Junior Year homeroom, mostly because he'd disliked that teacher the most and by junior year, you're seventeen and generaly curious as heck about yourself and other people. Sora would have been such a better date to his Junior Prom, and Senior Prom. But he had him now, and that was what mattered.