Preston Hill, 17, has been charged with sexual battery after he performed the move on another student during wrestling practice. Hill is also facing expulsion from Buchanan High School, which is just outside of Fresno.
The move calls for one wrestler to grab the other between the buttocks to turn him.
For Ross Rice, the father of the alleged victim, the move went a little too far.
"This kid basically targeted my son, pinned him to the ground and assaulted him," he said.
Rice said his 15-year-old son was painfully penetrated for at least 30 seconds by his teammate's fingers during a wrestling drill last year.
Hill claims he was taught the butt drag by his coaches.
"They're sweating and grappling with one another," said Charles Magill, Hill's attorney. "There is a certain amount of give and take that's involved when you're in that type of an intimate sport. We defended by saying that the conduct that he's alleged to have done is overblown and completely out of context with what happened."
Encino's Crespi Carmelite High School wrestling coach Mike Odman says the butt drag is a legal move, but he would never teach his students to penetrate an opponent with their fingers.
"There's nothing in wrestling tactics that would say when in doubt, insert," Odman said. "That never comes into play."
The alleged victim told police the older boy made a threatening gesture to him before they wrestled, a claim Hill denies.
Legal analyst Dana Cole says a jury will now have the tough job of determining whether this incident was premeditated.
"The judge is going to have to instruct the jury just what a sexual battery is and whether there was sexual intent in connection with this case," Cole said.
The boy says results from a doctor's examination prove he was slightly injured after the incident.
The trial starts Thursday in Fresno County. The accused student is also fighting his expulsion.