Students from every grade level gathered outside Brackett High School Tuesday for a ceremony honoring Madison and Marley Koontz.
The sisters and their parents were killed Friday on the way from San Antonio by an alleged drunken driver in a big rig going the wrong way on Highway 90.
Their 13-year-old brother survived.
"It hurts, but we're all getting through it together as a family," said Dolores Garza, a student.
The brief ceremony began with a song about angels, written for Madison and Marley, and a rendition of "Amazing Grace," followed by a moment of silence.
By then, everyone in the crowd was holding blue and white balloons, many bearing messages of sorrow at their loss and gratitude for their friendship.
"Everybody be ready. Let's send these balloons right up to heaven," said Kevin Newsom, the school principal.
At the count of five, the balloons floated away into the cloudless midday sky, to the sound of cheers and applause.
"It finally just let me let go of everything that's been going on," said Kaitlyn Partlow, a student. "I know I won't be able to bring them back but I know they're going to be here no matter what."