Bill started his high school coaching career not in basketball but as the freshman football coach at St. Mary’s High School where his teams went 30 - 0. He also initiated the first competitive boys golf team at St. Mary’s. In 1975, Bill was named head basketball coach at Paradise Valley High School where he coached until 1998. His Paradise Valley teams won state championships in 1995 and 1997, were state runners-up in 1994 and region champions nine times. His teams posted nearly 200 wins and an overall winning percentage 60%. From 1991 through 1997, Bill received numerous honors for his coaching success, including being named the Arizona Republic State Coach of the Year twice and Region Coach of the Year several times. He headed the USA Junior traveling team that competed Throughout Russia and Estonia and coached several players that were named All-State, All American and/or Player of the Year. In 2005, the PVUSD Governing Board voted to name the Paradise Valley High gymnasium the ‘William Farrell Gymnasium’ in honor of his 30 years of dedication and service to their athletic program.