Not if the boy was post-pubescent. If his body is biologically ready for sex, then what she is guilty of is a culturally manufactured crime, i.e. we as a society have decided that because she's a teacher and therefore in a position of authority over a young student, it's wrong for her to have sex with him. We have also set an arbitrary age (usually but not always 18 years) whereby we consider the young person a minor, or a legal child; a definition that disregards biology.
Of course, many fucking idiots out there are completely incapable of critical thinking and like to use highly charged emotional language (i.e. "this chick is a pedophile plain and simple") without regard to its technical validity in order to express their displeasure at the actions this teacher has allegedly performed.