This parent's experience is all too common among those whose children with special needs move from mainstream primary to secondary school, the Cambridge university study found.
Children with special needs are left bewildered by the speed of the secondary school day, struggle to cope with moving from class to class, and have to adapt to an unfamiliar peer group in a less controlled environment.
Secondary staff are rarely adequately prepared to deal with special needs pupils despite the good intentions of special needs co-ordinators charged with liaising with feeder primaries.
The report said: "Parents often described the erosion of self-confidence in their children after a few weeks or even days in the 'big school'.
Sometimes the change was dramatic and occurred within a relatively short space of time."
For many children, feelings of insecurity at this time produce a downward spiral of deteriorating behaviour. Official figures show children with statements are nine times more likely to be excluded from school than their peers.
"Outward expression of unmet needs often takes the form of extreme forms of behaviour," the report said.
"This can be particularly disruptive, not only disturbing to other children but also causing teachers to worry about children putting themselves at risk. This risk can exist for children of all ages but assumes different forms as the child gets older."
For some children frustration and insecurity leads to self-destructive behaviour. One assistant head of a secondary school described how a pupil was found "whirling like a dervish in a busy road", oblivious to the traffic.
The report warned schools facing such problems have insufficient support from mental health services. Diagnosis of mental illness is infrequent and there is too little recognition that children of all ages can suffer from anxiety and depression.
Staff often had to take counselling and social welfare roles without proper training or knowledge of where young people could get the right professional help, the report said.
John McBeath, one of the authors, said: "For a child with very complex needs to be put in a situation which is totally inappropriate for that child can be a form of child abuse."
The problems faced by children are compounded because teachers under pressure cope by handing over their care and education to learning support assistants.
The researchers found that some teachers, particularly those in secondary schools, had very little knowledge about special needs pupils in their class because they spent so little time with them.
Despite the introduction of guaranteed non-contact time, teachers lacked sufficient time to prepare materials suitable for special needs children.
This in turn exacerbated behaviour problems.
The report said: "If inclusion means anything it is the right to be taught by a suitably qualified teacher. Currently that principle is frequently breached."