The study, commissioned by the Secondary Heads Association, found headteachers were becoming frustrated by the amount of time staff were spending attending external interviews. An average of 14.5 teaching days were lost in 1998 on interview rounds.
The research also found huge inconsistency in the amount of time devoted to the selection process, particularly in the appointment of headeachers.
In one case, where the chair of governors was a personnel director of a company, a head was appointed after a one-hour interview with a panel of five.
The interview process in other schools lasted three days.
SHA general secretary John Dunford said: "Schools need to balance the thoroughness of their appointment procedures with the time that candidates are taken away from their current jobs. The interview processes should not last more than two days."