It has to vary. I made Head of Dept in both English and Art (long story), but the family costs were too much and I am best face-to-face with children, so I voluntarily relinquished monetary returns and, to start with, went on 'Supply' teaching. Turned out that I was very good at that so I did it for a while. One of my schools then employed me more-or-less permanently as general subjects teacher for over 10 years and the work/life balance sorted itself out (pension is practically non-existent, however :( ).