The brutal beating of Josie Lou Ratley on the campus of Deerfield Beach Middle School was not the act of an insane person, but the calculated crime of an angry young man intent on murder, a Broward jury ruled on Monday.

It took jurors four hours to deliberate a guilty verdict and reject the insanity defense of Wayne Treacy, the former Deerfield Beach High School student charged with attempted first-degree murder with a weapon. In March 2010, Treacy threw Ratley to the pavement, then repeatedly slammed her head against the ground and kicked her in the head with steel-toed boots because she sent him a taunting text message about his dead brother.

Treacy, 17, sat expressionless as the court clerk read aloud the jury’s verdict in a Broward Circuit Court room. He faces a maximum sentence of 50 years in prison, and a minimum of 15 years.

After the verdict, Ratley’s family issued a statement through an attorney expressing gratitude to jurors and prosecutors.

“We want to thank the jury for seeing the truth and doing justice,’’ the statement read. “It is not a day to rejoice, however. This is a tragedy for all involved. Thank you to the jury for having the courage to make the right decision. It is one more step on the road to moving on with our lives as best we can.’’

For Treacy, life will continue without the intense psychiatric treatment that he needs but likely will not receive in prison, said Russell Williams, Treacy’s defense attorney.

“You still have a mentally ill child,’’ he said, adding that his client has been under suicide watch in jail. “There is nothing to do for him but throw away the key.’’

Maria Schneider, the assistant state attorney prosecuting the case, said she was satisfied with the jury’s verdict. But she added that, given the youth of Treacy and Ratley, who also is 17, “This is one of those cases where it’s difficult to be joyful.’’

Schneider said she hoped one message will resonate with young people following the trial: “I hope they realize because you’re angry, because you’re upset, because you have issues, it’s never OK to take matters into your own hands.’’

Though Treacy showed no expression when the verdict was read, Williams said his client was “kind of shocked.’’

Williams said he plans to appeal the verdict because his client’s defense was hampered by Broward Circuit Judge David A. Haimes’s ruling that the jury could not watch and hear a two-hour interrogation video of Treacy conducted in the hours following the attack.

Judge Haimes ruled that Treacy’s statements in the video, in which he claims to have blacked out during the attack and that he only meant to scare the girl, were considered hearsay and self-serving. He said the defense could not present Treacy’s statements to the jury without giving prosecutors a chance to cross examine him.

Treacy declined to testify in his own defense, but his attorneys said he was in the grip of a hypnotic “dissociative episode” when he attacked Ratley. Both were 15 at the time of the attack.

The dissociative episode, a psychiatrist testified at trial, was triggered by a text message Ratley had sent Treacy on the day of the attack telling him to “go visit your dead brother,’’ whose suicide Treacy had witnessed in October 2009.