Daniel prepped under head coach Todd Dodge at Carroll High School in Southlake, Texas, which won the 5A Division II state title in 2004, 2005, and 2006. After playing his sophomore year at wide receiver, Daniel was a two-year starter at quarterback, leading his team to a 31–1 record. He completed 65.2% of his passes for 8,298 yards and 91 touchdowns and added 2,954 rushing yards and 39 scores. Southlake earned a No. 1 national ranking in 2004 after winning the 5A state championship, while Daniel won the 5A state Player of the Year. He was also named the EA Sports National Player of the Year.