Because Chio teachers, and its not often you get to see one, looks much prettier and more attractive than the most chio gal in school...
Maybe bcoz the teacher is more mature, and something like forbidden fruit taste best...
That time got one really pretty relief teacher come in, think she waiting for A lvl result or something, no guys in class even bother to look at the girls at all lor... During Lect and tutorial all wan sit in front row..

Its not really juvenile insecurity, prehaps more of a inferiorty complex among females.