Before the Andrew Jackson Elementary School’s Eagle Honor Choir performed for more than 50,000 fans at Nashville’s Nissan Stadium during CMA Fest on June 9, the third- and fourth-graders from Old Hickory, Tenn., got a surprise pep talk from Carrie Underwood.

Carrie stopped by the choir’s rehearsal in advance of their performance of her anthemic song, “The Champion.”

Under the direction of music teacher Franklin Willis, the students released a music video for “The Champion” in May, which caught Carrie’s attention. The school is a grantee of the Country Music Association’s nonprofit arm, the CMA Foundation, which works to ensure every child has the opportunity to participate in music education.

“I can’t wait for you guys to crush it on Sunday,” says Carrie. You guys are gonna be so amazing. That crowd is not gonna know what hit them.”

Watch Carrie surprise the kids below.