Dream Traveler Lina
Shin lu
Maybe.........Each student have their own bathroom. The Host Club probably got Haruhi or all the patrons put their money together and bought her one.

An I also have a question why don't Nekozawa know that Haruhi's a girl?
No one in the school but the Host Club know that Haruhi's a girl.
Opps, I meant like the girls donated money for a cute host club member that doesn't have money. Wait did that sound right? *shrugs*

or

She probably doesn't use the bathroom during school hours, or just waits until she gets home(i do that....i have a VERY bad school bathroom memory which cause me not to use public bathrooms...)