A horizontal ridge runs around the school's entire ground floor at an even height of about three and a half feet. It could be a design feature, but in fact marks the high water point, the join between the damaged lower section that had to be cut away, and the rescuable upper section.
At one point when the rotting wall had been removed but not yet replaced, says Kevin Beaton, the headteacher, you could look underneath the surviving wall and see from one end of the school to the other.
Sydney Smith School isn't quite so well ventilated now, but it's been a long, hard slog. The school, a secondary in Hull, was one of the worst hit by last summer's floods. Sited on a flood plain and lower than the nearby road, it had no defence against a fortnight's rain that had saturated the earth.
A total of 104 classrooms, offices and other rooms, including the library and main hall, were flooded. Equipment, books, resources and furniture were sodden. Heartbreakingly for Year 10 pupils, an entire year's coursework was destroyed.
"I hadn't realised how much damage water can do," Kevin says. "I knew the floors would be ruined, but I didn't appreciate we would have to cut out the walls because of the bacteria in the water."
Rebuilding work began almost immediately, with pupils who couldn't be accommodated on the upper floors decanted to sites across Hull for the last weeks of the summer term. Last term began a week late, but by then the school could house all 1,600 pupils, with the help of 19 temporary classrooms.
Builders are still toiling, but it's gradually getting back to normal. Only a handful of classrooms are out of use, the library is being restocked and about to reopen and most of the damaged equipment has been replaced. The hall is a mess - Kevin hasn't been able to hold an assembly since the flood - and both it and the remaining classrooms will not be completed until next term.
Clare Carter, a food technology teacher, says practical work last term was largely confined to studying equipment, disassembling it and putting it back together. The pupils couldn't cook, nor could they do anything that would need clearing up.
The school has been asking exam boards about extending deadlines for coursework - "There's absolutely no way we're going to be able to meet them," says Clare - although nothing has yet been decided.
Since moving back into her classroom at the beginning of this term, though, Clare says things are looking up. "Some of the equipment we were using was from the 1960s; at least now I've got a new room and all the equipment is new."
A year's GCSE art coursework for about 120 pupils now in Year 11 was destroyed in the flood. "When it comes to their final exhibition, we won't see the full impact of their abilities. They feel really deflated," says Dionne Ruffy, head of art. Resources accumulated over many years were lost.
The art department moved back this month after spending last term in mobile classrooms, where no running water meant pupils had to use chalks, pastels and pencils, with painting or modelling too messy.
The repair bill at Sydney Smith, met by the local authority's insurers, is expected to be about pound;5 million. "The staff have put up with some tremendously difficult circumstances and they have coped remarkably well," says Kevin. "The silver lining is that the ground floor has been refurbished and we will be able to direct the money we would have spent doing that into other things."
Bengeworth First School, in Evesham, Worcestershire, also sits on a flood plain, but unlike Sydney Smith, where the flood is seen as a one-off, it has flooded before. David Braham, the headteacher, a veteran of the 1989 flood, knew the importance of doing repair work straightaway. The waters rose - again as the ground became too waterlogged to absorb any more rain - on the last day of the summer term, but the school still managed to reopen only two days late for the autumn term. "They were painting and decorating right down to the last minute, but at least we now know we can do it in six weeks," says David, who was project manager for the pound;750,000 refurbishment.
"We're now back to normal and the beauty of it is we have got a brand new school and I've been able to buy the latest schemes of work."
Knowing the school could flood again is behind a number of design changes. The boiler was badly, and expensively, damaged, so its replacement is on a raised floor with the burner on top, to hopefully keep it safe.
New cupboards are all on wheels, so they are easily moved, and the tables are stackable, forming a high platform for books and other resources. Power points have been raised, although it was only the ones where equipment was plugged in that were damaged.
David has also picked up a valuable tip for the next flood: much of the damage was caused by condensation on the hot days immediately following the downpour; airing the building before the water has subsided could save valuable equipment.
It was the day after the end of term when rainwater sped down a sodden hill into St David's Primary in Moreton-in-Marsh, Gloucestershire. Parts of the school ended up almost five feet underwater. The heating and the electrics were ruined.
Six months on, the 240 pupils are being taught in temporary classrooms while repairs are carried out. It is expected to be completed by Easter at a cost of pound;2 million.
"The temporary classrooms are very well equipped, although they are quite cramped," says Bob Forster, headteacher. "The staff have been fantastic in getting everything up and running."
As at Bengeworth, power points are being installed at waist height to reduce future damage, but Bob says strengthening flood defences may be the best option for a low-lying school that will always be vulnerable.
By contrast, Bryn Hafren Comprehensive in Barry, south Wales, lies around half a mile above sea level. But this was not enough to protect it from the flood water that rushed down the neighbouring hill on the last day of the summer term.
Although it reached a relatively shallow 18 inches, it caused about pound;1 million worth of damage, with the risk of mould meaning plaster had to be replaced, and condensation destroying about 140 computers.
Six large temporary classrooms were set up while repairs were carried out with the building ready to be fully occupied just before Christmas, says head Phil Whitcombe.
The risk of a repeat at Bryn Hafren is not considered enough to implement major changes or flood defences, although the local authority is looking at improving the drainage. "It has never happened before and I hope I'll retire before it happens again," Phil adds.
That sinking feeling
A total of 857 schools in England with about 360,000 pupils were affected by the floods last June and July. A further four were hit in the Vale of Glamorgan, south Wales.
Of the English schools, 201 were assessed as needing significant repairs and another 26 suffered severe damage requiring the use of temporary classrooms.
The Department for Children, Schools and Families announced grants of pound;10 million for schools and children's services in response to the June floods, plus pound;4 million for the areas hit in July. Cash was allocated to provide temporary accommodation, surveyors and summer activities for children flooded out of their homes.