Of course, if you are promoting a set of GCSE maths books then the person you need to reach is the head of maths. If you can reach the other maths teachers also teaching GCSE in the school, so much the better.
But if you are selling photocopiers, scanners, or other office equipment it is vital to get to the administrator, school business manager, and/or bursar in the school.
Yet many companies ignore this vital sector in schools, and as a result these individuals get only a fraction of the promotional material others get.
For example, there is a growing interest in schools at the possibility of following the NHS in moving across from paper records (requiring as they do multiple filing cabinets that take up a lot of space, and providing a significant risk of being lost through mis-filing or fire) to a digital record system. But some companies have tried to promote this to headteachers, who are not primarily concerned with the need for more space in the school office. It is always important to reach the people who will be affected by an issue, as well as the ultimate decision-maker.