Why are scissors, of any size, a prohibited item at a school? Does the school provide only plastic/round scissors to its students? I can think of a lot of reasons a 10-year-old (about a 4th grader) would need for 8-inch shears. Cutting heavy posterboard or fabric for a project comes to mind.

The cop should be fired for needlessly traumatizing a child. The teacher and administrators involved should probably be fired.

This mentality is very scary because students who grow up in this sort of sanitized, terrified-of-everything, "weapon free," environment are more likely to tolerate and even welcome unreasonable searches in their adult life. At age 25 they might find it perfectly acceptable if the Boston transit authority decides to ban scissors and knives of any size and search/SSSS all pax at each station.