The IHP program was based on a program at Walter Reed Middle School in Los Angeles, California. Khrystyne Haje (Simone Foster) was an actual graduate of the Reed IHP program.
At the time of his departure, it was speculated that Howard Hesseman left the show for a revival of his former show WKRP in Cincinnati (1978). However, that was not the case as he didn't reprise his former role on the The New WKRP in Cincinnati (1991), which debuted in the fall after the cancellation of Head of the Class (1986). Ultimately, the reasons for Hesseman's abrupt departure were never revealed. However, Hesseman did express his dissatisfaction about the direction of the show and his character's lack of development in several interviews during the show's run.
By the final season, Dan Frischman, Tony O'Dell and Michael DeLorenzo were all over 30 years old and playing high school students.
In a 1998 interview on The Roseanne Show (1997), Sir Billy Connolly said that he had a beard when he was cast, but he had to shave it off because ABC had done tests and found people perceived men with beards as "sinister" - a theory also used by Disney (the owner of ABC) in their hiring process.
Howard Hesseman left the series at the end of season four. Sir Billy Connolly took over the lead for the fifth and final season.