The 36-year-old singer fought back tears from the first moment of her powerful speech, delivered directly to those watching at home.
"I'm a Texas girl, and my home state has had so much heartbreak this past year," Clarkson said. "Once again, we're grieving for more kids that died, for just absolutely no reason at all."
The tragic shooting, which is believed to have been committed by a 17-year-old student who attended the high school, claimed the lives of 10 people, eight children and two adult teachers, and left 13 others wounded.
"Tonight they wanted me to say that, obviously we want to pray for all the victims and we want to pray for their families, but they also wanted me to do a moment of silence," Clarkson said, wiping tears from her eyes. "I'm so sick of moments of silence. It's not working, obviously. So, why don't we not do a moment of silence? Why don't we do a moment of action? Why don't we do a moment of change? Why don't we change what's happening? Because it's horrible."
The heartfelt and defiant call to action elicited a supportive cheer from the crowd, after which Clarkson continued, "Mommies and daddies should be able to send their kids to school, to church, to movie theaters, to clubs. You should be able to live your life without that kind of fear."
"We need to do better," Clarkson added. "Because we're failing our children, we're failing our communities and we're failing their families. I have four children; I cannot imagine getting that phone call or that knock on the door."
Clarkson and husband Brandon Blackstock share two children -- 3-year-old daughter River Rose and 2-year-old son Remington Alexander. The singer is also stepmom to Blackstock's two children from a previous marriage, 17-year-old daughter Savannah and 11-year-old son Seth.
"So, instead of a moment of silence, I want to respect them and honor [the victims]," Clarkson said. "So tonight, in your community, where you live, let's have a moment of action. Let's have a moment of change."