You enter most country houses through a grand front door. At Erddig the way in is through the estate yard, past the joiner's shop, blacksmith's shop and wagon shed.
That's the first surprise. The second is the number of the pictures of servants on the walls. Carpenters, gardeners, housekeepers, blacksmith and a "Negro coachboy" are immortalised in portraits or photographs, each with a piece of doggerel verse written by one of the Yorke family, who owned Erddig from 1733 to 1973.
This emphasis on life below-stairs makes this late 17-century house and its out-buildings, situated just south of Wrexham in Clwyd, a rich resource for social and historical exploration, and one that is much used by schools.
The Living History programme is extremely popular. "It's not a question of children just looking," says education officer Jill Burton. "Here they can touch, smell, taste, and generally be fully occupied."
Today, groups of boys and girls from a Clwyd primary school are scattered around the servants' quarters, all nattily got up in authentic Victorian costume, and absorbed in their tasks.
In the spacious New Kitchen, where a motto on the wall exhorts them to "Waste Not Want Not", one group is grating lemons for Miss Penketh's Lemonade. In the attic another is making beds, emptying chamber pots (no, just cold tea), and beating carpets.
In the laundry a third group is scrubbing and rinsing sheets. The boys take part without a murmur. "You're next on the mangle, Andrew," the laundrywoman and guide calls out. A lad in 1885 cap eagerly takes a turn at squeezing the water out. Children can also dress in servant's costume for a tour of the house, which they are shown as if they were applying for a job. Tucked behind doors are boxes of objects relevant to servants' tasks, which the children can handle as they are shown round by the butler or the housekeeper.
Some curiosities above-stairs include a Regency harp lute, an Edison phonograph, a euphonium, a splendid Gothic organ and a pneumatic musical disc player. The house is also full of good examples of 18th and 19th-century furniture and fittings.
And then there's the nursery, containing a rocking horse, an early doll's house, a wooden toy train, and a Noah's Ark with animals. This being Wales, none could be touched on Sundays - except the latter, as they feature in the Bible.
Who can now believe, wandering through this glorious Elizabethan house and its majestic gardens, that 60 years ago it was on the point of being demolished? Today Montacute House, its elegant proportions and pleasing symmetry carved out of honey-coloured stone, is a jewel in the Somerset countryside. And within is another jewel: a stunning collection of pictures on loan from the National Portrait Gallery .
An outstanding example of Renaissance architecture, Montacute was built at the end of the 16th century by Sir Edward Phelips, a successful lawyer who later, as Speaker of the House of Commons, prosecuted Guy Fawkes over the Gunpowder Plot. The family owned it for more than 300 years. That "very superior person" Lord Curzon was briefly a tenant (Elinor Glyn, his mistress, helped redecorate the house). In 1931 Ernest Cook, grandson of the travel agent bought it for the Trust.
The house was then virtually emptied. Today its rooms are filled with fine examples of furniture, ceramics and glassware, from Elizabethan times and later. There are rare tapestries, a good collection of samplers and, bizarrely, Lord Curzon's bath. Some rooms are a surprise. The library, so often sombre, is light and airy, its windows containing the original heraldic stained-glass. The nude female statues at the sides of the original chimney-piece, shown in an illustration nearby, were thought indecent by the Victorians, and removed.
The function of rooms changed over the centuries. The library was once the dining-room, the dining room the buttery. The Great Hall - actually modest in size - was for greeting rather than eating.
There are many paintings: Dutch, Italian, French, English, including two by Sir Joshua Reynolds. But the huge NPG collection in the long Gallery - used by the Phelips family for exercise on rainy days - puts these in the shade. Here are pictures of all the English monarchs from Henry VIII to Charles I, and many portraits of those who wielded power behind the throne. Here too are poets Wyatt and Surrey, and playwrights Ben Jonson and Beaumont - but not Fletcher.
Educationally it's a treasure-house, not just for history, but for costume design (the clothes are quite dazzling) and art techniques. "There are endless possibilities," says Clare Gittings, the NPG's education officer, who runs courses for teachers. "You can do a lot using the portraits as historical evidence, showing how such powerful people used their images."
With his crew cut and black bomber jacket, the 10-year-old boy seemed an unlikely volunteer. Yet here he was happily trying on a milking yoke at the invitation of a Victorian milkmaid.
Such sights are commonplace at Wimpole Hall near Royston in Hertfordshire, where the Trust runs an ambitious Living History scheme linked to the farm on the estate. It was built in 1794 as a model farm, to show new ways of growing crops and breeding animals. It includes a magnificent Great Barn, now housing a fascinating collection of tractors, threshing machines, ploughs, root cutters, and other machinery. On this working farm children can observe a rich variety of rare breeds, from the Anglo-Nubian goat to the kind of sheep used by Neolithic Man. There are also opportunities to see lambing, as well as silage production and harvesting.
The extensive 350-acre park, created by Capability Brown and others, provides a rare example of the medieval "ridge and furrow" farming system. The varied woodland and ponds around the estate are much used for outdoor study.
In the hall Living History focuses on the servants' quarters: the steward's room, the housekeeper's room and the butler's pantry provide authentic settings for historical re-creation.
Built in the 17th century, the hall's main rooms reflect the preoccupations of its successive owners. Most dramatic is the domed Yellow Drawing Room; but there's also a stunning library and book room; and a fine gallery, used for balls and the staging of plays by the children of the house. Victoria and Albert were guests here in 1843. One of the many excellent educational resources is a copy of the Cambridge Chronicle, providing absorbing details of the royal visit.
Other more homely rooms reflect the taste of Elsie Bambridge, daughter of Rudyard Kipling, who leased and then bought the hall in 1938 after her father's death. On his only visit her father told her: "You've bitten off more than you can chew."
The results of her travels and forays into the saleroom are in rooms such as the South Drawing Room, full of elegant furniture and pictures of all periods. Drawings and engravings she and her husband collected - including some deliciously subversive Gillray cartoons - are hung in what used to be her bathroom.
Education officers Jane Munns and Annetter Razey have added two new activities: Victorian costume sessions, showing what both servants and gentry wore, and handling artefacts of the period. Both innovations are suitable for primary-age children.
Ormesby Hall belonged to the Pennyman family for over 450 years before passing to the trust in 1961. The last occupant of this chunky, attractive sandstone house, set in a 275-acre garden and park outside Middlesborough, would have approved of the educational use to which it is now put.
Ruth Pennyman had no children, but was interested in other people's. A devotee of the theatre, from the 1930s onwards she staged semi-professional productions of Shakespeare for local children, using the house's fine 18th-century stables.
She and her husband James were landowners with a social conscience. During the Depression, when Teeside was blighted by unemployment, they set up co-operatives and small holdings for local people, and established a joinery business which mass produced Art Deco furniture.
The couple were only following a philanthropic tradition. In the 19th century the estate was run as a model Victorian enterprise, with two new churches, a model village, a cottage hospital and a village school.
Details of the later ventures, and of daily life at Ormesby in the 1930s, have been preserved in interviews with people who worked there as servants. Their reminiscences provide an intriguing glimpse of the responsibilities of the hall boy, maid, footman and others.
Some duties were unexpected. The hall boy had to wash the family's two golden retrievers. He also was charged, after the butler had fired at the noisy rooks in the trees, with dealing the fatal blow to any merely injured bird.
One focus of Living History activities at the Hall is below stairs. Another is changing technology: children work in the kitchen and laundry comparing the efficacy of Victorian gadgets - mangles, food mixers, water filters, hot-water bottles, knife sharpeners - with those of today. "By doing simple experiments, and using the artefacts, they can understand not just how things work, but why they were necessary," says education officer Jenny Deacon. "We also get them to look at whether mechanisation is a good thing or not."
The main building is mostly Georgian and provides splendid examples of the restrained Palladian style. Since it's been left as it was in Ruth Pennyman's time, almost every period is represented in its paintings, furniture and other objects.
The result is pleasingly eclectic: in one room you come across a Reynolds portrait, in another two lamp fittings which the much-liked owner bought for 7s 6d each in the Portobello Road.
Well-established country house seeks housemaid, footman, kitchenmaid, launderess and coachman. Will suit persons wishing to gain experience of domestic service in times gone by. Apply Lewis Bunting, Butler."
This mock advertisement kicks off a Living History project recently begun at Felbrigg Hall, near Cromer in Norfolk. Children dressed in period costume and equipped with life-histories are interviewed by the butler and housekeeper, and learn of the tasks required of them below-stairs.
"There's nothing like feeling your arms ache from stirring the butter or doing the laundry to bring home what people's lives were like," says education officer Carrie Lawson. "It makes so much more impact on children than reading a book or watching television."
For much of its 375 years of existence, the hall had a full complement of servants. Its domestic rooms are well-preserved: the kitchen with its charcoal stove, the steward's room, and the butler's pantry with its spacious cupboards for quantities of glass and plate. Since the fine main building went up around 1620, two wings were added as well as an orangery, a stable block, a dovecote, a magnificent 18th-century walled garden, a lake, and extensive park and woodlands.
Much of the educational work covers art and design. The wealthy Windham family, who owned Felbrigg until 1863, employed fashionable interior designers for additions and alterations, and the rooms offer a wide variety of architectural styles. Many are highly ornate, with lavish plaster ceilings, roccoco mirrors, and elaborate wallpaper. The Cabinet room is stuffed to the ceiling with paintings: William Windham II did the Grand Tour and brought back many oils and gouaches from Italy.
The impressive library several books given by Dr Johnson, a family friend - they include his Iliad, Odyssey and New Testament - and contains some austere but beautiful tall wooden bookcases inspired by the Gothic revival.
Carrie Lawson is alert to the dangers of a surfeit of treasures. "I object to children touring the whole place with a clipboard," she says. "It's better if they concentrate on one room, or work on one particular aspect in detail. "
Felbrigg also offers scope for work out-side. A woodland walk might involve identifying trees, birds and animals; learning to map read; or helping trust staff to plant trees. There are wetlands, water habitats and natural grassland; and a chance to see 18th-century conservation methods in action.
To find out what's going on in a National Trust property near your school contact your regional education officer.
Details from the education department at the Trust's head office. Tel: 0171 222 9251.
Erddig, Clwyd: 01978 313333 Montacute House, Somerset: 01935 823289 Ormesby Hall, Cleveland: 01642 324188 Wimpole Hall, Hertfordshire: 01223 207801207257 Felbrigg, Norfolk: 0263 837444