As we walk briskly around the grounds of the Welsh Folk Museum, education officer Walter Jones offers a warning: “Some schools come here to see everything, and end up seeing nothing. You have to have a focus to benefit from a visit.”

You can see his point. There’s a stunning variety of things to see at Britain’s first open-air museum, one of three major institutions of the Museum of Wales. Set in a hundred acres of parkland at St Fagan’s in the Vale of Glamorgan, it provides a rich and absorbing microcosm of life in the principality over the past 400 years.

The big attraction is undoubtedly the extraordinary collection of more than 30 original buildings. Farmhouses, cottages, shops, workshops, a tollhouse, a cockpit, even a circular pigsty, have been moved here from all parts of Wales, and carefully re-erected to show the living and working conditions of the Welsh people at all levels.

The wealthy are represented by the one building that belongs to the site, St Fagan’s Castle, actually an Elizabethan manor house built within the walls of a Norman castle. Donated to the Museum of Wales by the Earl of Plymouth in 1947, together with the gardens and grounds, it is now furnished like a great Welsh mansion of the early 19th century.

At the other end of the social scale there is a row of six cottages used by miners and their families in Merthyr Tydfil when it was the world’s most important iron manufacturing town. Each of the tiny dwellings shows the gradual changes in the buildings, their contents and their gardens between 1805 and 1985, reflecting the boom and slump of different periods.

Several buildings house working crafts people, some of whom have spent most of their working life there. There’s a miller, a baker, a potter, a tanner, a blacksmith, a saddler and a wood turner. For children there’s a wide range of real activities on offer, from mixing daub to spinning and grinding corn, from making a pot to using a pole-lathe.

Another feature is a one-room 1880 Victorian school, transported from Lampeter in West Wales. Here, Walter Jones dons the appropriate costume, hands out quill pens and blotting paper, and gives children a taste of table-chanting, class-reading and drill in the yard. “There’s no instruction, just terror, ” he says with a smile.

In the past there have been criticisms of the Museum of Wales’ schools service, which has not always been seen as important within the institution. But now, with new exhibitions and galleries in the main building in Cathays Park in Cardiff, and a more integrated education service or stream, there are many more opportunities for hands-on and creative use of the themuseum’s exhibits by schools.

One of the main building’s greatest assets is its extensive art collection, which includes a wonderful and much-studied haul of French Impressionist paintings, housed in one of the six newly refurbished galleries. Aside from these works - by Pissarro, Renoir, Monet, Van Gogh, Sisley and Cezanne - there aregalleries full of examples of virtually every period of British and European art.

When working with children on the paintings, art officer John Rowlands aims to elicit their personal responses. One recent project, linked to key stages 1 and 2 in art, music and language, encouraged pupils to produce art and written work and music, inspired by the work of Stanley Spencer, Allen Jones, Michael Andrews and others in the collection.

An exciting new exhibition covers the Evolution of Wales. It’s bang up to the minute in its use of sound, light, film and artificial landscapes to chart the evolution of the world, with Wales as the centre of attention. Another recent addition is the Man and the Environment gallery, with stimulating interactive exhibits.

Change is also the order of the day at the third of the museum’s main institutions, the Welsh Industrial and Maritime Museum, with its spectacular view across Cardiff Bay, soon to be transformed when the controversial barrage is in place.

The museum houses exhibits relating to the area’s industrial past: engines, buses, trams, steam vehicles, early forms of bicycle, a lighthouse, a ship’s bridge, and figureheads including that ofCaptain Scott’s Terra Nova. It organises many events and temporary exhibitions, including Steam Days on spring and summer Saturdays.

The Museum of Wales’ education service, co-ordinated by Rhina Jones, provides plenty of materials to help teachers, including education packs and activity sheets. There’s also advice and training on the use of the museum’s resources, on planning visits, and on material for school projects.

For schools that find visits difficult or expensive to organise, there is a travelling museum, staying a fortnight in each area, and aimed especially at providing hands-on experience for primary school pupils across a range of subjects.

The museum also fulfils its national remit through its specialist museums and galleries dotted around the country. These cover the Welsh slate and woollen industries, the Roman occupation of Wales, the work of 20th-century painter Graham Sutherland, Welsh power, and Welsh art.

* National Museum of Wales and its branches: Main building, Cathays Park, Cardiff CFl 3NP. Tel: 01222 397951 Welsh Folk Museum, St Fagans, Cardiff CF5 6XB. Tel: 01222 569441 Welsh Industrial and Maritime Museum, Bute Street, Cardiff CFl 6AN. Tel: 01222 481919 Turner House, Plymouth Road, Penarth, CF6 2TH. Tel: 01222 708870 Roman Legionary Museum, High Streets Caerleon. Gwent NP6 lAE. Tel: 01633 423134 Amgueddfa’r Gogledd, Llanberis, Gwynedd LL55 4UR. Tel: 01286 870636 Welsh Slate Museum, Gilfach Ddu, Llanberis, Gwynedd LL55 4TY. Tel: 01286 870630 Segontium Roman Fort Museum, Beddgelert Road, Caernarfon, Gwynedd LL55 2LN. Tel: 01286 675625 Museum of the Welsh Woollen Industry, Dre-fach Felindre, Llandysul, Dyfed SA44 5UP. Tel: 01559 370929 Graham Sutherland Gallery, Rhos, Haverford West, Dyfed SA62 4AS. Tel: 0437 751296.