I was called in to see the teacher just a few days after my son, Alex, started school. The teacher said he wouldn't sit at his desk. He was five years old and we had just suffered a sudden bereavement in the family. I tried to explain how he might be feeling but she didn't seem to want to know."

For Anne Cranston, this was the beginning of a several years of difficult parental consultations. "It's very upsetting hearing teachers be negative about your child. I would sit on the little chairs in the classroom and I wouldn't know what to say."

Teacher after teacher described a pattern where, long after the other 29 children had started writing, Alex would still be scrabbling about in his pencil case, or where the teacher would look over rows of bent heads to find him staring out the window without having written a word.

The least distraction in the class would be enough for him to stop work and it would take a lot of teacher time and effort to make him start again. When a young teacher took to putting his desk out into the corridor, the Cranstons moved Alex to a private school.

Compared to some of the problem behaviours that children can exhibit in schools, Alex's might seem relatively minor. After all, most children spend some time daydreaming and get distracted. But according to Jackie Ravet, an academic at Aberdeen University, this pattern of "disengagement" is the biggest source of stress for teachers and an under-recognised problem for schools.

Children who become chronically disengaged like this are very difficult to reach, she argues. They underachieve and many teachers find the daily struggle to keep such children on task daunting and unrewarding. Children who become disengaged in primary can fare even worse in secondary where this kind of behaviour is less tolerated and can escalate into something more serious.

Ravet studied the phenomenon with 10 "disengagers" in a small school in the north-east over a complete school year. These were all children who seemed "perfectly bright and capable" and had no diagnosis of specific needs. Yet all of them expressed negative feelings about school, often complaining of "boredom". Two talked about "hating" their teachers who, they told Ravet, frequently shouted at them.

Ravet has recently been publicising her findings in educational journals and discusses the study in the most recent edition of the British Journal of Special Education.

She found that patterns, which may have started as early as a child's first day at school, had become entrenched and both pupils and teachers were stuck in a vicious circle. Teachers did not want to spend all day battling with these children and in some cases were at their wits end. Several resorted to a persistent, low-level "nagging" which Ravet concluded was ineffective or could even make the problem worse, further damaging the relationship between teacher and pupil.

The children told Ravet, through drawing and talking, how they were using their behaviour as a "survival strategy" to rescue them from despondency. For some of them, school had become a "profoundly sad and depressing" experience. They were aware that they were falling behind their peers but didn't feel they could do anything about it.

They resorted to their difficult behaviours - which included flicking paper balls at the ceiling, chatting, starting ruler fights, wandering around and day-dreaming - because they found them more satisfying than what the teacher was asking them to do.

At the same time, many felt nervous and fearful of getting into trouble, yet trouble didn't stop the behaviour, which had become part of a cycle. The ratio in Ravet's study was nine boys to one girl, a typical gender balance, she says.

Many of the children, however, responded better to active learning experiences and became most disengaged when doing writing tasks.

Ravet found that the only children who made progress in the year were in the class of an "exceptional" teacher who had found a non-confrontational way of dealing with three of the children. She worked lunchtimes and in the evening with these children and their families, spoke to them about their feelings and was able, to some extent, get them back on board. These three ended the year taking some responsibility for their own learning.

These three boys "adored their teacher", according to Ravet, who adds: "One boy, David, noticed that she never told him off when he was chatting but would quietly come over and sit near his table. She also gave him more time to do the work and regularly said well done'".

Ravet argues that primary teachers must be encouraged to go the extra mile with disengagers as early as possible, talking to them about their emotions and trying to bring them back into partnership in the learning process. "It is hard to gather statistics on disengagement. It means different things to different people. In some classrooms, children are allowed to chat quietly and walk around. In others they are not. Some children disengage in the upper years of primary, some on their first day. But if you ask teachers what their biggest source of stress is, it is these children who don't seem to want to learn."

However, Ravet found that most of the teachers in the study blamed the home environment for the children's problems and few were aware of the children's feelings about school. Parents could end up like "piggy in the middle"

if they weren't encouraged to be honest about their children's feelings about school.

Professor Eric Wilkinson of Glasgow University's department of education believes the teaching profession needs to give this issue more focus. "It is a huge problem, lamentably so. It needs more focus in primary because by the time a child starts secondary it is almost too late."

He argues that classroom practice is part of the problem, citing Edinburgh as an example. "Edinburgh is a case in point. The council has imposed a regime in the early years of primary where the whole morning is spent on literacy and numeracy. But the children never see a real book.

"They spend the whole time working on their letters and numbers on magnetic boards and I think by the end of the morning some of them are tearing their hair out.

"This is about getting the right kind of leadership into our schools. There also has to be real communication between schools and parents, and that means schools being more welcoming and making more of an effort to talk regularly to parents.

"It also means parents seeing that their responsibility continues after their child starts school. It doesn't suddenly end when the child enters the school gate."

Jackie Ravet's book about her study, Are We Listening, is published by Trentham Books. The names in this article have been changed.