It is the moment every parent dreads: the day when their child leaves the relatively intimate, known world of the primary school and enters the big unknown of the secondary. From now on, they're on their own.
Most children seem to make the transition quite happily, often helped by special programmes and familiarisation days between feeder primaries and the secondary. If they transfer to secondary with a raft of friends, the move is all the easier. After a bewildering few weeks, they know their way around and have sorted out the system.
However, a sizeable minority of children don't: the newly-arrived, the shy, the vulnerable - the ones who have just about hung on through primary school but now come unstuck.
Sir Alan Steer, the Government's pupil behaviour tsar, believes it is at this transition stage that children can "get lost" and attainment and behaviour start to go seriously wrong. But is the real problem for these children that most secondary schools are just too big? Mental health experts believe the answer is yes.
"I feel quite strongly that large secondary schools are such noisy and threatening places, that for children who are less than robust they are a very frightening place to be," says Dinah Morley, an ex-social worker, teacher and former deputy director of Young Minds, the mental health charity. "They're a nightmare for an adult, let alone a small child."
Vulnerable children simply cannot get the one-to-one attention they need in a large school, she says. "Able and reasonably well- motivated children can get on OK. But in an inner-city school, you may have 20 per cent with English as a second language and 10 to 20 per cent with a mental disorder. These are not the kind of problems that will go away after a nice chat with Mum."
Dr Tharu Naidoo, who worked for 23 years as consultant child and adolescent psychiatrist for the north London borough of Haringey, says in her experience it is children with social, behavioural and learning difficulties who struggle most in large, mainstream schools. "In the old days of special schools, it was children of normal intelligence but with a physical disability who got a really lousy deal," she says.
"Now, with a policy of blanket inclusion, the ones facing greatest difficulty are those with learning problems such as a language disorder, or with severe emotional and behavioural problems, especially if they are immature and can't fit in with their age group socially."
So how big is too big? Research on the effects of school size on attainment and behaviour is inconclusive (see box on page 17), but a great deal hinges on factors ranging from the socio-economic nature of the area to the quality of management - and especially pastoral care - of the school.
The consensus among experts suggests that between 500 and 800 pupils is a good size for a secondary school to meet its pupils' social and emotional needs. Some would say smaller: Dinah Morley says "500 to 600 top whack" and Jane Thomas of the charity Human Scale Education thinks that even a school with 500 pupils is starting to push individuals to the edge.
Sitting neatly within the 500 to 800 range is Abbeydale Grange in Sheffield, an 11-to-16 comprehensive with 620 pupils. With a constantly shifting population - more than 30 per cent of pupils arrive after the start of the school year - Catherine Bull, the headteacher, is grateful that it's not too big.
"Seventy per cent of our pupils come from ethnic minorities and 50 per cent have English as a second language," she says. "Some have no English when they come. We pride ourselves on the fact that we can assimilate children quickly. It helps to have a small school with a strong pastoral staff.
"As the headteacher, I know an awful lot of children and families. And a full-time member of staff acts as a mentor, liaising with families before pupils come and keeping an eye on them for the first month or so. We teach one group of Slovak-speaking Roma separately, with a primary timetable, and go out on home visits too."
One in three pupils at Abbeydale Grange has special learning needs. But Catherine says that the school also challenges the more able pupils and takes pride in the fact that all but three out of 153 Year 11 leavers continued in education or training last year.
The irony is that Abbeydale Grange, originally a comprehensive with 2,000 pupils but now the smallest secondary in Sheffield, has been under threat of closure by the local authority for the past 15 years. But, with its position strengthened by its new media arts specialism, the school is planning great changes to make its scale even more intimate. It will reorganise itself into four vertical groupings, with mixed-age tutor groups of only 20 children.
Brislington Enterprise College in inner-city Bristol is at the other end of the scale, with 1,200 pupils when it opens this Monday. Its numbers are scheduled to swell to 1,755, but the pupils will feel they are attending something much smaller. That is because Brislington is the first school to be completed under the Government's Building Schools for the Future programme on the schools-within-a-school model.
"We're moving children into five core learning communities, with up to 300 children in each," says John Matthews, the headteacher. Two will cater for Years 7 and 8 and two for Years 9 to 11, with a separate community for the sixth form. In addition, there will be a unit with 20 places for physically impaired pupils and another for children with autistic spectrum disorders.
Pupils will spend about three days a week in their learning communities, with the remaining two days spent on curriculum areas requiring more specialist facilities, such as science. Each community will have a head and 16 staff, including six teachers - two maths, two English and two humanities.
There will be no more tutor groups. Instead, each pupil will belong to a learning family of 10, which will meet a learning guide (a teacher, assistant or administrator) for a 20-minute chat at the end of the teaching day. The adoption of this model - which comes after visits by the head to the high-achieving small schools of Boston and New York - follows the school's move towards a competency-based curriculum better suited to individual children's needs. It is the last stage in the school's remodelling to provide education on a more intimate scale.
Why such radical change? "Four years ago we conducted a survey of parents and carers and the thing that came back was that many thought it was too big," says John.
"People were not convinced that individual needs could be met in such a large institution."
The ethos of the school still harked back to the one prevailing in 1999, when John arrived at the school as deputy head. "At just under 2,000, we were historically the biggest in Bristol - a large, urban comprehensive where you had to be resilient to be successful. But we did not have the quality of relationships we might have had."
The aim now is to make sure that pupils have high quality relationships, he said.
Jane Thomas, a former secondary teacher, says the schools-within-a-school model has the advantages of large and small schools. It allows the staffing and resources to offer a wide range of options, thus meeting the Government's standards agenda, while also promoting the individual care that is at the heart of Every Child Matters. But the mini-schools have to have genuine autonomy, Jane says.
Anything that makes school units smaller and less daunting looks like progress, says Dinah. "At the moment, we plan schools for the average, able, contained child.
"We have to plan for the growing number of vulnerable children, who need a much more nurturing environment. Without that, they cannot begin to achieve."
Small is best for Casey
"Casey" is just the kind of pupil who should never have found herself in a large secondary. "I got on all right in my first year at primary school, but then it got harder," is how she sums up her early experience of education.
She was, in fact, severely dyslexic, but this was not diagnosed until she was in Year 6. By then, her mother had become too ill to look after her and she had started moving around, interspersing periods of foster care with stays with her grandmother.
Casey's attendance became irregular. But she was relatively settled and living with her grandmother when she moved on to secondary school; a 1,400-pupil comprehensive in a town on the south coast.
"It seemed very big," she says. "There were probably 30 in the class and I never really had a chance to talk with my form teacher.
"I got a bit of help with my dyslexia. But the lessons didn't really help - they were teaching me things totally opposite to what I'd been taught before."
After a relatively calm Year 7, Casey started to get into more trouble. She spent more spells in internal isolation for truancy or smoking and was suspended several times for disruptive behaviour - answering back, walking out and arguing with other children.
"People started taking the mick out of me because of my problems with reading and I started getting angry," she says.
Finally, she was permanently excluded. Then she struck lucky. Her local authority sent her as a last resort to the Serendipity Centre, an independent special school in Southampton with a capacity of only 15 pupils. Having come from a large school, this felt more like a family. There are only two in her class and lots of support of every kind. And most of the pupils, like her, are in care.
"It's really good," she says. "The teachers are closer to you and we all stick together."
The average size of English secondaries has been creeping up in the past 10 years, from 850 in 1997 to nearly 1,000 pupils now. Only a third of English secondaries have fewer than 800 pupils. Nearly one in 10 publicly- funded secondary schools in England has more than 1,500 pupils. A handful have more than 2,000 and at least one has more than 2,500.
It is often assumed that pupils achieve better results in smaller schools and behave worse in larger schools. But so many factors are at play - history, intake, resources, management, popularity - that this cannot be shown to be generally true.
A Government-funded review of research on school size four years ago found that the larger the secondary school, the better pupils' results and attendance tended to be - up to a certain point. But the researchers could not say from the evidence what optimal school sizes for results and attendance were.
All the studies did, however, show that pupils felt less and less engaged with schools the larger they became.
Source: Secondary school size: a systematic review (2004), available on www.eppi.ioe.ac.uk.