For plot purposes, it sort of kills the whole challenge. If everyone just broke their pens and was able to walk away, it wouldn't be much of a test and the whole segment would be null. The I-men are supposed to test the student's combat abilities foremostly; the faculty probably would have precautions against certain powers.
While Ed's idea might've been an effective one in theory, we may have to rethink the way they recognize the pens (more biological thought-process?) or just leave it in the air and re-do it from the last post.