To give the adults a little credit, the students may have had more time to work on the mystery. The adults on the hiring committee were simultaneously holding d

To give the adults a little credit, the students may have had more time to work on the mystery. The adults on the hiring committee were simultaneously holding down jobs, maintaining homes, changing diapers, cooking for their families, etc. The hiring committee probably had deadlines for researching the candidates and making final decisions, whereas the students didn't have the same sort of time constraints. (I don't mean to minimize the achievement of the students! But you asked for factors that could have allowed the adults to miss this one.) The woman was probably fairly charismatic to pull this off. The hiring committee surely had several face-to-face meetings with her and was swayed by her charm. The students would have seen her 'fake principal' self rather than her 'job interview' self. They didn't get the full snow job, so they were perhaps freer to think more objectively. Also, I'm sure there's a false sense of safety in numbers for the hiring committee: if one person (or every person) had vague doubts, they might think, "Oh well, everyone else seems to think she's okay."