The photo itself is really good, just doesn't say grunge to me. And the tilt is too subtle. If you're going to use one, go for it! Right now it looks more like a mistake.
I scored this a 6... I love old school photography of old schools (grin)... I think the sky could have used some special attention as it, to me looked dithered more than grunge.
I think that while the overgrowth in front of the school can add to it's age and state of disrepair, it doesn't mean it makes it an overly grungy feeling shot. The lighting seems to bee too bright (check the roof), even in the false tones to convey a sense of a dark/brooding/grimy place.
I think if you had shot this with a longer exposure closer to dusk it would've felt creepier.
1/100 speed means you had a good amount of ambient light here to get this shot from this distance, that is evident in the roof and windows.