Coach Castillo begins his first year at Greenville High School and his 24th year in the coaching profession. Throughout his career he has made stops at Medina Valley, Mission, and Somerset High Schools, helping lead successful programs and playing a significant role in the turnaround of both the Mission and Somerset football programs. Over the past 13 seasons, teams he has coached have advanced to the playoffs 11 times. While at Mission High School, he was also recognized as the Dave Campbell's Texas Football Dairy MAX Assistant Coach of the week.

Coach Castillo's philosophy centers on treating  players and coaches with love, understanding, and respect while providing them opportunities to grow and become successful both on and off the field. At Greenville, that philosophy is represented through the M.A.G.I.C-Make A Great Individual Commitment. His believe is that becoming a little more committed each day can lead to tremendous success in football and, more importantly in life. 

Coach Castillo wants Greenville football to be know for playing fast, physical football, having fun, and competing with honor and respect. His goal is to build a culture of excellence in the classroom and on the field while helping everyone associated with the program leave Greenville equipped with tools and support necessary to become positive, productive citizens.

Coach Castillo and his wife, Leora, have been married 26 years and have three children: Carleigh, Nora, Myles. Nora is a junior at Greenville High School, while Myles is a freshman. Their oldest daughter, Carleigh, graduated from Somerset High School in 2022.