"Demolition High" is ridiculous on many levels. However, it made me laugh a bunch. It seemed less like a fully thought-out movie and more like an exercise in putting actors into scenes. "Hey, we could have Corey shoot something out of a fire extinguisher!" "Yeah, and Melissa could walk menacingly up these stairs!" "Wait, we could use this circular saw for something..."
What surprised me was that somehow the movie managed to include the absurd as well as occasional moments when the actors and the writing made me care a little bit about the characters. I've always like Corey Haim, for whatever reason, and even though this whole film was a transparent vehicle for him to play a role (and not a very convincing role), I still rooted for "Lenny Slater". I also liked a few moments with some of the supporting cast, certainly more than the shaky script and acting would suggest.
Ultimately I give this a 5. It's laughable in many ways, but that was part of the fun. When Corey grabs a machine gun and runs *past* the injured Melissa, out of the room, down the hall, and *then* turns and fires randomly back at the room they squared off in, you can't take this seriously and you can't believe any of them did either. So just relax and enjoy the comedy, be it intentional or not.
P.S. I had to "fix" this review because my original summary of "LOL" was interpreted as shouting -- even when I added periods. :-)