Like a blind date, a call to an unknown supply teacher could lead to a beautiful relationship - but is it worth the risk? It's both galling and counterproductive to bring in a weak teacher, so we often cover absences internally, despite the disruption this causes to those who have to alter plans at short notice.
As a special school, we have the additional problem of a traditional reluctance among teachers to come in to a special school. Some good teachers just don't have the confidence. Some just don't have the skills to think creatively about the daily problems children with special needs face in accessing learning experiences most take for granted.
To overcome this we decided to organise an open week for supply teachers. Our local authority agreed to contact all teachers on their supply list with our invitation and our letter excited considerable interest.
We offered: * A 30-minute talk, covering the children, the staff, the organisation and our philosophy. We wanted to make it clear that, despite the children's special needs, we deliver the full breadth and balance of the national curriculum - and that where there are problems, they lie in the inadequacies of the system, not within the pupils.
* A walk around the school to see facilities which make most mainstream colleagues a little green with envy.
* An hour in the classroom of their choice - perhaps most important for us and for them.
* A cup of our excellent coffee. The response was overwhelming. We met lots of teachers, some clearly desperate for work. By the end of the week we were turning people away. The week went very smoothly, with more than 20 teachers spending a morning at Millwood.
The week also clarified for us what we look for in a supply teacher.
* Reliability: experienced supplies work at the drop of a hat, any time, in any class. Those who booked appointments but didn't arrive - and there were several - clearly blotted their copy books, and missed the chance of work in the future.
* Technical skills: can the teacher manage the class efficiently, follow someone else's plans, but bring in a little extra? Technical skills are best tested in situ, which is why we offered a chance to work for an hour in a classroom.
* Personal qualities: an overriding consideration. How does this person relate to children and to other adults? It means adaptability, a balanced ego, and the ability to relate spontaneously to a child.
We had three tips for supply staff offered an opportunity to show off their skills on a visit to a school.
First, show professionalism, and be remembered, perhaps through a CV. Though we suggested to many that they brought an A4 sheet about themselves, so we would remember one from another after the event, very few did so. Second, smile. And third, turn up on time: it's a buyers' market.
An open week is a very easy way to meet a lot of supply staff, and to find out who you would ask back. In these days of person specifications and objective criteria for jobs it's a rather old-fashioned way of working. Unfortunately, making permanent appointments using pre-defined criteria can be like an arranged marriage: though everything may be all right in theory, it may not grow into anything special. Trying out supply staff is like living together first. There's less risk, and either side can withdraw more easily.
The week was a real exercise in mutual selection. Those who responded self-selected by showing an interest. Of those who visited, some clearly decided this was not for them.
This left us with a core of enthusiastic teachers. We knew who we liked, and within a couple of days two of them were working for us. One who returned to get a bit more experience has made it on to our new shortlist, from which we will develop our new supply pool.
Bernard Emblem is headteacher and Joan Hall deputy head at Millwood School, Bury, Lancashire