A: Normally, a school will advertise any post. However, apart from head and deputy head posts, adverts do not need to be in the national press. The school could just put a notice on the staffroom board. It will depend on the governing body's staffing policy, and a local agreement may cover recruitment procedures.
It is generally good policy to advertise every post but I can understand why a school does not, especially if it feels there is already someone doing a good job and an advertisement might not bring in other candidates. If the person acting up has relatively little experience, the school may feel that it should advertise. The acting head may accept that they have gained valuable experience, but not be ready for a long-term commitment. Staff should be promoted because of their capabilities - not just for years of service.
Heads and governors have to juggle many different issues when taking these decisions. Although the market for newly qualified teachers is currently well supplied, the same is not true for heads of department. In the past year, more than a third of secondary schools in London looking for a new head of mathematics have had to re-advertise. So, as the saying goes, a bird in hand may be worth two in the bush.
John Howson is a recruitment analyst and visiting professor of education at Oxford Brookes University. To ask him a question, email him at email@example.com.