Swift also shared a video of three-time NBA winning coach Steve Kerr, who broke down during his pre-match press conference.
Kerr, 56, refused to talk about basketball and instead pushed for gun control.
"When are we going to do something," Kerr shouted at his pre-game press conference.
"I'm tired. I am so tired of getting up here and offering condolences to the devastated families that are out there. I am so tired of the, excuse me, I am sorry, I am tired of the moments of silence. Enough!"
In her tweet, Swift added: "Steve's words ring so true and cut so deep."
Countless celebrities have joined Swift on social media, with Marvel actor Chris Evans simply writing: "F***ING ENOUGH!!!!"
Initial reports indicated that 14 children had been killed, but that number has now risen to 19, with the total death toll currently at 21.
The incomprehensible tragedy occurred at Robb Elementary School in Uvalde, about 96km east of the southern border of Mexico and about 128km west of San Antonio.
Robb Elementary is a school for students in grades two, three, and four.
Authorities believe the shooter was a local 18-year-old man named Salvador Ramos who was a senior student at Uvalde High School.