A survey of 119 Scottish headteachers has found that almost half of them work 60 hours a week or more - the equivalent of working from 8am to 6pm every day, except Sunday, without a lunch break.
Only a few of the 100 deputes, who also took part, said they were keen for the top job. More than two-thirds (68) agreed with the proposition that going for a headship was not "an attractive proposition".
"Since this corps of people is where the next generation of headteachers will come from, it must be a matter of some concern that the headteacher post is perceived in this way by so many depute heads," according to researchers at Edinburgh University.
In an echo of warnings already sounded by headteacher organisations over problems with succession planning, the researchers concluded that "recruitment to these senior posts in future may be problematic".
Women appeared particularly reluctant to become headteachers; more than half of deputes are female but only a quarter are heads.
One possible explanation, the researchers suggested, was that women were just beginning to become prominent in senior positions and over time would continue to advance. But it could have been a conscious decision; deputes, having come close to seeing what being a head entailed, might decide against it.
Deputes did not work such long hours: a third said they worked more than 60 hours; half between 50 and 59; and a fifth fewer than 50.
Local authorities did little to lighten their load, the heads and deputes reported; both agreed that they introduced an unnecessary layer of bureaucracy and failed to add value. They were the most commonly cited "demotivating" aspect of the senior managers' work. One respondent referred to the "patchy support from local authority"; another to "the utter incompetence of my employing authority".
The most positive aspect of the teachers' agreement was the induction scheme, said heads and deputes. That apart, they struggled to find anything positive to say about the agreement.
"The flatter job structure and associated re-sizing process were problematic and have not offered opportunities to improve learning," said the researchers. "The teachers' hours agreement is not working well, especially in the opinion of DHTs; the chartered teacher scheme has not enabled staff to play a more important role; morale has not been boosted by the salary arrangements; and workload remains onerous."
Some senior managers spoke about people being "very conscious about job- sized roles, what they are being paid for, what they can be asked to do". It was also reported that an attitude of "clock-watching" had been engendered among a minority with the introduction of the 35-hour week.
Others described the job-sizing toolkit as "a farce", and divisive at depute headprincipal teacher level.
However, in spite of all this, heads were inclined to agree strongly that their job was the best in the school and they could make a difference. Most head-teachers (101) and deputes (81) were satisfied with their jobs. One female depute head reported being very dissatisfied.