First off, why is a 15 year-old still in middle school?
Anyways, based on the story given and the picture of the kid's "weapon", I definitely would not have thought twice about putting a few rounds into the little shit. First priority is protecting life and safety of the public and other responding officers.
From the article:
"Why was so much excess force used on a minor?" he asked. "Three shots. Why not one that would bring him down?"
His wife, who demanded that the officers be punished, added: "What happened was an injustice."
Who agrees with the parents? How many of you, when faced with a weapon pointed directly at you, would only shoot one shot to preserve the lives of everyone in a crowded school?
It states, two officers fired three rounds at the kid. I for one think that the proper amount of force was used. I was trained, as a minimum, to fire in controlled pairs (two shots at all times) for most situations. That being said, the answer to their question is, the amount of force was used on the minor because the minor pointed an extremely real looking weapon at the police officers. End of story.