Call For Help: How Do We Get Boys to Respect the Restroom?

At the last school I worked in, vandalism was so prevalent and the campus so overcrowded that the constant destruction of the boys' bathroom was not surprising. Tagging by graffiti "crews" (interested only in graffiti as art) or actual gangs would cover the walls, mirrors and doors. Students would break parts of stalls and toilets, and break the towel and soap dispensers off the walls so rapidly that new ones wouldn't last a day. At one point, they would alternately lock bathrooms or simply not replace things for a long time.

In my current school, tagging isn't an issue, but the bathroom is a disaster. Besides people peeing all over the toilets and floors (and usually not flushing what actually gets inside the bowl), every few days all of the toilet paper and paper towel rolls are shoved into every urine-filled toilet. A door was broken off its hinges as well. This was actually a new bathroom after the old ones were closed due to students causing flooding in one and taping the garbage can to the ceiling in the other (among other incidents).

My question is simple: how can we get our male students to respect the bathroom? There's virtually no vandalism outside of it, and even if you put the destruction to the side for a moment, it's still disgusting and messy all the time.

1. If you've had this particular problem at your school, what has been successful in addressing it?
2. Have you had similar issues elsewhere at school? What has been done that has worked?
3. How do we build a sense of ownership and responsibility for our school in this case, and in general?

I'm looking forward to your comments. Any idea is appreciated!