8am: Am very excited as I have succeeded in securing a day's supply at South Wales's premier private school. As I walk through the gates, amid a sea of daisies, and gaze at the beautiful open parkland that lies to the side of the school, I am aware that this is going to be a completely different experience. Cue for a choir of angelic voices, as a crocodile of very small pupils in dark green uniforms complete with tartan kilts marches past me, in pairs, on their way to the chapel.
I am given a warm welcome at reception by a begowned master, who sweeps me into the staffroom and plies me with lashings of fresh filter coffee. "Please avail yourself of coffee and biscuits at breaktime, and at 1pm luncheon is served for staff in the dining hall." This a far cry from the usual "don't touch our mugs or our coffee" approach practised by many state secondary schools.
11.30am: There is a slight hitch with the double-booking of a studio between a harpist and a group of GCSE IT pupils. However, I am impressed that the matter is resolved with the minimum of fuss. The pupils exude an aura of serene self-confidence, obviously the product of a background of staunch parental support and affluence. Am constantly reeling from the fact that they are all so polite to me and each other!
1pm: Lunchtime. Walk into old-fashioned black-and-white tile-floored dining room staffed by congenial dinner ladies. Have enormous salad, which is delicious and healthy, but am tantalised by the large, steaming jugs of custard.
At the pudding counter, I am transported straight back to my childhood. A large metal tray of gooseberry tart cut into squares smiles up at me. Oh bliss! Take proffered square smothered in bright yellow custard and demolish with relish. The grail that is the traditional school pudding has not been lost. Have not seen gooseberries for so long that I thought they had probably become extinct; another casualty of climate change.
Instead of whisking themselves back to the staffroom, the teachers sit at a specially designated table among the pupils and chat happily while enjoying the fruits of a free lunch. Yes, apparently there is such a thing after all!
It is a sharp contrast to my familiar jostle in the sandwich queue, with pupils eyeing me belligerently as I "push in" and squander at least #163;2.50 on a sad, squashed-looking roll and a bottle of water. As one of the teachers leans over and asks a pupil to refill the copper water jug, I wonder just how long they would survive in some of the schools that I've experienced.
3pm: It is the last lesson of the day. Year 7 geography. I have been left a DVD to play them about earthquakes. Like many schools these days, the classroom is equipped with a large interactive whiteboard, which can only be written on with an electronic pen and upon which you can show downloaded items from the internet and, of course, DVDs like a home cinema system. This is so much better than trying to cram about 30 pupils around a tiny TV with a dodgy volume control.
While the DVD plays, one boy is trying to tell the others in stage whispers all about earthquakes. The class become restive so I move him next to me. "I only wanted to explain it better to them, Miss," he says disconsolately.
"So you're interested in earthquakes are you?" I ask him.
"My dad's a seismologist," he says proudly.
"Well, my dad's an astrophysicist," says one of the other pupils
"And my mum is ..." joins in one of the girls. I leave them arguing the various merits of rocket science over geology. When I was at school we used to boast that our dads were policemen.
4pm: The bell goes and I dismiss them, row by row, out into the dying rays of the sunlight. I walk down the spiral staircase and can almost hear the thudding of a thousand footfalls that have thundered down them decades previously. Pigtails flying under straw boaters; a whirling medley of arms, legs, kitbags and musical instruments.
I glance at the photographs on the oak-panelled walls, dating back to 1913. The boys so carefree in their striped rugby shirts, all too soon to be substituted by the drab green-brown of the khaki uniform.
Outside, a regiment of shiny 4x4s awaits. Behind the wheels, bronzed and beautiful yummy mummies eagerly scoop up their offspring, ready to transport them to an endless merry-go-round of ballet classes, tennis tournaments and cello lessons.
Jo West, Supply teacher, Cardiff.