After graduating from Notre Dame High School, John DeCoster attended classes at Los Angeles Pierce College. He later studied at California State University Northridge where he received a Bachelor of Arts degree in English.
In 2007 John and his wife Nancy have been married for 43 years. They share three sons. Their oldest Matt (42) lives in San Francisco with his partner, also named Matt. They have been together for 13 years. The DeCoster's son Adam and his wife Elaine live in Van Nuys, with John and Nancy's grandchildren Isabella and Luc. John says, "Adam is a hockey fan, and named his son after a hockey player. Where did I go wrong!"! The DeCoster's youngest David is 38 and lives in Redondo Beach, California.
John taught high school English for 42 years. In 2007, he is teaching one or two classes a semester at the College of the Canyons. Nancy and John lived in a mobile home in Santa Clarita. John calls the town, "God's waiting room."
In his leisure, John likes to golf, ride his bicycle, read, watch movies and television. He and Nancy enjoy going to plays and symphonies and going out to dinner. John likes to play low stakes "Texas hold 'em" in Gardena and often shares activities with other Notre Dame graduates. Between these activities he sneaks in his naps.
John relates that he has several "claims to fame". Among these are winning a $2 bet from O.J. Simpson while playing golf with Dan Zerfas at the Riviera Golf Club (Dan is a member). He plays golf with Hugh Johnson (NDHS 1958), "brother of our most famous alum". John appeared, for about a minute, on the television show Criminal Minds, "because I facially resembled a serial pervert."