User blog comment:B214/Kuoh Academy students finding out that Issei stays with the ORC girls and is dating Rias./@comment-24098614-20131215011722/@comment-16281343-20131215075600

What do you mean by he has no choice? He has lots of options where he can change clothes.. ie: the room where he was sealed?

Well.. as much as we like to speculate whether they do know or not, there is not much that we know about Gasper's interaction with the students in the school.