Sandy Hook 'Over the Rainbow' tribute song available on Amazon, iTunes (LISTEN)

Children who survived last month's shooting rampage at Connecticut's Sandy Hook Elementary School have recorded a version of "Over the Rainbow" to raise money for charity.

Twenty-one children from Newtown, Conn., performed the song Tuesday with singer-songwriter Ingrid Michaelson on ABC's "Good Morning America." Most of them are current and former students of the school, where 20 first-graders and six staff members were killed.

They recorded "Over the Rainbow" on Monday at the Fairfield, Conn., home of Chris Frantz and Tina Weymouth, two former members of the Talking Heads and Tom Tom Club rock bands.

Watch the video at the bottom of this story.

Copies went on sale Tuesday on Amazon and iTunes , with proceeds benefiting the United Way of Western Connecticut and the Newtown Youth Academy.

Kayla Verga, 10, said she was singing for a friend, 6-year-old Jessica Rekos, who was killed in the massacre.

"Singing the song makes me feel like she's with me and she's beside me, singing along with me," Kayla told "GMA."

Another girl, 10-year-old Sandy Hook student Jane Shearin, added, "I really want to be kind to the people who have lost their loved ones and help them to recover from their sorrow."

Gunman Adam Lanza went on a shooting spree with a semiautomatic rifle in the school on Dec. 14 after having killed his mother at their home in Newtown. He fatally shot himself as police arrived at the school. It's still unclear what motivated the attack.

The Sandy Hook children have returned to classes in a neighboring town at a building renamed for their old school. Newtown officials and residents have begun discussing what to do with the school where the shootings occurred.

Some parents of children killed in the massacre spoke out on Monday, calling for a national dialogue to help prevent similar tragedies.