He is now back teaching, at a special school in Wellingborough, having laid up the red tails and shiny black top hat. But the bug persists: his son has taken up with a circus as a unicyclist and juggler.
Mr Hasler's experiences are not likely to be repeated by any teacher today. Not that circuses aren't the fascinating, compelling places they always were, and teachers, like other folk, still sometimes seek adventure. But the difference is that few if any local authorities still employ teachers to travel around with circuses, providing mobile schools.
From 1984 to 1988 Northamptonshire paid for Mr Hasler to teach the circus children, gave over a capitation allowance, "and the circus did all the rest," he explains. "I taught all the artiste's children, from age zero to 16, both those from abroad who were here temporarily and those based in England. "
Before his appointment, circus children would pop up at a new mainstream school each week, often 200 miles away from the previous one. It was disorienting, Mr Hasler believes, for everybody. "A circus child would come into a new school and every teacher would down tools and say 'let's do a project on travellers.' A week later, the child would move on to another school with similar ideas."
Children in circus, traveller or Gypsy families have traditionally missed out on mainstream education because of the logistical complexities of their lives, as well as the paucity of support for travelling parents.
Today, more are being educated at mainstream schools than ever before, supported to varying degrees by education social workers and education welfare officers. There are, needless to say, those children who will go out to work if the family has a small business or trade. And there are also those who neither work nor go to school, living on the fringes of society. There are distinctions between the three groups: circus children travel with their parents and may perform themselves. They generally winter in the South and then, from the end of March, go travelling. Gypsies in this country are defined as an ethnic group of English and Welsh people who originally descended from India. Among themselves many speak an Anglo-Romany dialect. Travellers are of Scottish and Irish descent who organise themselves around specific trades. Their dialect is Anglo-Cant, derived from a form of Gaelic. Both groups are proficient in English.
In the West Midlands, a regional consortium of 10 local authorities provides education for more traveller, Gypsy and circus children than anywhere else in the country. It is the only thing of its kind; elsewhere, local education authorities work on their own. The West Midlands consortium's education service has a fluctuating number of between 1,500 and 2,000 travelling children in its schools during a school year.
Pat Holmes, the service co-ordinator, reckons that one-third of the eligible families in the consortium's wide catchment move around more or less continuously. Contrary to widely held beliefprejudice, this does not prove travellers' fecklessness. Rather it is often because of frequent eviction from temporary sites. Complaints from the public about illegal encampments result in travellers being forced to move elsewhere by the local authority. Invariably, that elsewhere is another temporary site. It is a practice that is common to all local authorities in the country.
You do not have to be an expert in traveller culture to understand the human toll this shunting around takes, for teachers as well as the travellers. "This greatly undermines family security and it is disruptive to mainstream teachers when children are evicted," Ms Holmes says. Given the frequent movement of families, one of the priorities of the consortium's education service is to create strategies that will help to bring continuity to these children's education. To facilitate this aim, schools ensure that children's school records follow them to their new schools. In-service training is provided for teachers on issues relevant to travelling children and care is taken by the participating local authority departments to move families shorter distances, to avoid children having to change schools so frequently.
Of course, families will move further afield when the circus moves on or when local job prospects dry up. But until then, the idea is to provide a modicum of constancy in the children's lives.
Teachers are supported and trained to be realistic about their time with travelling children. Ms Holmes says: "They don't have to make up for all the time a child has missed schooling. It's important to get teachers to see themselves as part of a network in the child's schooling experience - even if only for a week. People have to see a child's time in school as important, no matter how short that time actually is."
Added to the difficulties of transience is the image of the traveller or Gypsy in our culture. Prejudice against the stranger suddenly appearing in their midst is not the province of any one group in a school: such feelings can run from the head down to teachers, pupils, parents and auxiliary staff and will often be stoked by the local community's invariably negative response to illegal encampments. In such an atmosphere, it may be hard to make a child feel welcome. But there is a flip-side to the stereotype of the traveller child for their mainstream classmates that verges on the exotic - as someone who is as free as the wind with no responsibilities, no rules to follow, no harping at home to do homework or practice the piano. It's like Never Neverland with caravans.
Neither picture, of course, is true. It is also untrue to generalise about how travelling children live and how they manage with their lifestyles. Ms Holmes says: "Some handle movement better than others. It's our organisations that don't have the strategies for dealing with mobile communities." She cites the common travelling community as being comprised of large, viable extended families in which children grow up resilient, confident, capable and curious. It is when they settle in one place that they may feel less sure of themselves.
The consortium provides distance learning materials for the small number of circus children in the area when they go touring in the spring and summer months. Otherwise, the focus is on "bringing this community into the statutory education system," Ms Holmes says. It is not an easy task and the numbers of older pupils is still proportionately small, but more young people are staying on in school each year, even to the point of taking their exams. Whether more would be doing so with on-site schools is another question.
What the law says.
The obligation for local authorities to provide education for travelling children is enshrined in a number of laws.
Traveller children, including Gypsies, are specifically dealt with in the Education Act 1980, Department of Education and Science Circular 181, which emphasises local authorities' duties in this respect, regardless of the legal status of the camp site in which the families base themselves.
The Department for Education has allocated a specific grant (under Section 210 of the Education Reform Act 1988) to the consortium for the purpose of improving levels and enrolment and attendance of travelling children and to facilitate their access to the national curriculum.
Section 199 of the 1993 Education Act states that parents whose children do not attend the school at which they are registered are guilty of an offence.
However, there are circumstances in which transient families of "no fixed abode" will be acquitted, including when "the child has attended school as regularly as the nature of the parents' trade or business permits."