What does “significant” improvement mean? Is it five more points on the GCSE A*-C score, fewer exclusions or improved teaching and learning? And when does the clock start ticking? From the day Ofsted pronounces the school in special measures, the day the report is published, or the day after the old head leaves? With only a year in which to turn things round, every day counts.

There is a national shortage of people applying for headships. Does Ruth Kelly really think her pronouncement will persuade high-flying, experienced heads to leave secure jobs to try to transform a school in special measures in a year? You have to be a risk-taker and like a challenge to be head of a school in special measures, but this is taking things too far. If you weren’t successful, the school would be closed and you would be out of a job.

I was seconded to run a secondary school in special measures for two terms while a permanent head could be appointed. From my experience, all you get in one year is “quick fixes”; sustained improvement takes three to five years.

There is a simple recipe for turning round a school, but it is a long time in the making. It goes like this. Take a huge dollop of discipline to restore order and promote good behaviour. Add a good helping of morale-raising activities, a sprinkling of modifications to the curriculum and a large recruitment campaign to help the quality of teaching and learning to rise. Mix well and bake for about two years over a background of resistance from students and parents and intransigence from the LEA.

Any school in special measures has complex problems; it didn’t get like that overnight. In some cases, years of underinvestment and mismanagement need to be overturned. Many such schools suffer from significant staffing problems: an over-reliance on supply teachers, overseas-trained teachers and unqualified teachers, and a large number of staff on long-term sick because of stress. Experienced, well-qualified teachers aren’t queuing up to teach in schools in special measures.

Quick fixes don’t last. One academic year is not enough to significantly improve the chances of examination success for most Year 11 pupils. Many of them will have been taught badly for years, be disaffected, and lack good study habits and GCSE coursework. How is a head supposed to bring about significant improvement for such students? All you can resort to are stunts such as bribing the students with a pound;200 reward if they achieve five or more A*-Cs, safe in the knowledge that any payout is not going to make much of a dent in the school budget. Assuming Year 11 students do, by some miracle, get improved examination results, you can’t keep repeating the exercise year on year. You have to address the underlying problems.

Discipline is easier to fix but rarely straightforward. The irony is that headteachers are under pressure from government to keep exclusions down, but without removing disruptive pupils it is extremely difficult to restore order. It is quite common for independent appeal panels to overturn the head’s decision to permanently exclude, thereby giving that child and all of the other disruptive students in the school the equivalent of a “get of out jail free card”.

Don’t get me wrong. Schools in special measures have an obligation to improve as quickly as possible. What I object to is the idea that one size fits all. Some schools may be able to emerge from special measures quicker than others; it depends on the problems they face. Each school needs an individual approach, and this is best provided by the attached HMI. My inspector recognised the legacy of difficulties and the local context; he was supportive but also professionally challenging. I didn’t mind being challenged by someone who had been a head and knew what the job was really all about. Where does HMI fit into Ruth Kelly’s idea of closing schools in special measures if they don’t improve within a year; doesn’t she trust inspectors either, or does she think she knows best?

Nor am I against the idea of academies. There is a time and a place for them, but not at the expense of schools in special measures that are making progress and will come good in the end. Academies have not been tried and tested. Perhaps if the kind of money being thrown at them was given to schools in special measures, improvement would come faster.

Vanessa Ray is headteacher of Shenley Brook End school, Milton Keynes We do know what’s best