"It said thanks for the offer, to appreciate my enthusiasm," Shiley said of the letter, which was read to the boy's fourth-grade class.
Shiley's mother, Kris, said Michelle Obama's letter expressed appreciation that Shiley would be interested in helping the first family choose their new White House pet.
"It really thanked Zack for being kind and considerate, caring about the kind of dog the family was going to choose," Kris Shiley told the Tribune-Review. "(She said) it's nice to know that young children are interested in caring about other people in the community and outside the community."
The newspaper said the Obamas ultimately accepted a 6-month-old Portuguese water dog, they named Bo, from U.S. Sen. Edward Kennedy, D-Mass.
