The two main areas where this seems to be happening are English, which comes with responsibility for whole-school literacy, and mathematics and computing. As staff shortages in these areas continue at main grade level and among potential middle managers, more schools may be tempted to choose this option.
Most assistant head posts are on offer at somewhere between points 10 and 14 on the leadership spine - between pound;36,000 and pound;40,000. Even so, this is less than the top of the advanced skills teacher spine, which allows such staff to be paid up to a maximum of pound;44,000 - just short of point 18 on the leadership spine.
For a head of department who is already on the maximum of five management points, and stuck at around pound;36,846, the attraction of a further pay rise as an assistant head might seem seductive, providing the extra workload were not too onerous. In this case, it may well be that the competition for scarce staffing resources at middle management level will encourage more schools to go down this route.