An annoying group of ex-students from 'Monte Alto International High School' decide to spend a night in the now abandoned institution where a 'mystery' killer called the watchman played by horror legend Paul Naschy murders them off one by one."School Killer" features some references to such teen slasher staples like "Scream" or "Friday the 13th".The climatic twist ending looks like lilted from "The Sixth Sense".The uncertainty about whether the homicidal watchman is alive or dead provide some mild interest,but the characters are one-dimensional and the endless scenes of walking through dark school corridors really got on my nerves.The presence of charismatic Paul Naschy almost saves this clichéd slasher flick.There is also some decent gore on display including a splendidly bloody beheading.It's nice to see Manuela Velasco of "Rec" fame in a small role.4 out of 10.