Because of his toothy smile that rarely leaves his face, he was named "Smilin' Gabe."

Pruitt is reported to have began as a baseball player before switching to basketball, although during an interview with Joe Castiglione and Glen Geffner on WRKO during the July 2, 2007 Boston Red Sox game, he indicated that he ceased playing baseball in elementary school.

In high school, Pruitt averaged 22 points per game as a senior at Westchester High School in Westchester, California in 2004. He was a Parade Magazine fourth team All-America selection, and earned Roundball All-America, Student Sports All-America special mention, Los Angeles Times All-City and South Bay/Westside first team and South Bay Daily Breeze Player of the Year honors. He was listed as the No. 20 prep player in the country by Basketball Times after his senior year, and was considered among the top 20 prep guards by Athlon Sports and Insiders.com in his senior year in 2004.