The truth of the matter in this case as borne out by the assertions of MANY students at the middle school in question was that it was a game that was played among the students on certain days of the week. They called it "butt slap day" and guys did it to girls, girls did it to guys, the typical middle school stuff.
This whole issue has been huge in our local media for quite some time and what seems to be unclear at this point is what the teacher/s who originally reported the incident told the kids in the hours, days, or weeks prior to the incident being blown into a sexual harassment issue by the prosecutor.
"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting 'Holy Shit! What a ride!'" ~Hunter S. Thompson