At William Howard Taft High School, Dinwiddie was recognized as one of the greatest standout athletes since Jordan Farmar. He averaged 5.9 points and 4.1 assists as the starting point guard alongside a fellow 2014 draftee in DeAndre Daniels at the conclusion of his junior season. Dinwiddie maximized his game as he began his final year representing the school, averaging 11.2 points and 7.7 assists. He was one of the most skilled passers in school history, and became the John R. Wooden California High School Player of the Year in 2011. However, Long Beach Poly's Ryan Anderson was named California Mr. Basketball. Dinwiddie became just one of seven players that won the prestigious award as a senior. The powerful duo of Daniels and Dinwiddie won the city championship this season as well. This final season at Taft helped Dinwiddie gain the attention of colleges around the country. He chose to attend Colorado rather than Harvard, Oregon, Santa Clara, or UNLV.