CRAIGMOUNT High School, in Edinburgh, carved a unique niche in football history last weekend as the 100th winners of the Senior Shield, the world's oldest national schools competition. Spectators included captains of former winning teams, some of whom were in their seventies, among the guests of honour at a Hampden gala to mark the beginning of the centenary of the Scottish Schools Football Association.

Craigmount beat St Ambrose 1-0 in a match where the uncommitted must have felt some sympathy for the Coatbridge team. They lost the blue riband under-18 final for the third time in four years.

The trophy, donated by Queen's Park to what is recognised as the oldest national schools FA in the world, has been played for every year, including the war years.

Over the past century, the SSFA has evolved from fairly modest origins to become a highly-developed organisation, according to secretary Richard Thomson. ''At one end of the spectrum there are small-sided games for young primary children,'' he said, ''while at the other there is high-profile international exposure against such diverse teams as Brazil, Germany, Italy, France, Holland, United States, New Zealand, Morocco, Israel, Iceland, Liechtenstein, and England.''

Only last week the Scottish U16 side returned from Northern Ireland having won the Ballymena International Tournament, against teams financed and coached by their professional national bodies.

Craigmount's head, a former physical education teacher, is one-time Newtonmore shinty star John Fraser, and sport has a high profile at the 1300-pupil school. One 14-year-old, Louise Pate, broke the 100m butterfly record at the schools inter-national in Wexford last week, while another, Claire Masterton, won the vault with the highest score ever as the school's U13 team represented Scotland at a gymnastics international in Stoke.

The issue of persuading PE staff to fulfil extra-curricular duties, however, is reflected in the confession by school sport spokesman Sam Lynch that only two teachers involve themselves with running the school's five age-group football teams: ''We rely heavily on a number of parents who give us outstanding help.''

Craigmount have won half a dozen trophies this season, but last night lost the chance of another. Local rivals St Augustine's beat the Senior Shield winners 3-2 on penalty kicks after extra time in a play-off for the Lothians U18 league title.

A professional golfer, a snooker player, and a snow boarder are among recent Craigmount former pupils, but Manchester United player Michael Stewart is currently the best known. They can also claim former Ranger Lee Robertson, now with Start, in the Norwegian second division, and Craig Lynes, recently freed by Dumbarton. Claire Crosbie, a member of the Scottish Women's FA squad, will go to the US on a sports scholarship when she leaves this year.

Bernard Fagan, the manager of St Ambrose, was himself a former Senior Shield winning captain, with St Patrick's High in 1965, and St Ambrose also have a record of kicking off the careers of successful senior players, most recently Celtic's Tom Boyd, and Malky Mackay, now with Norwich.

The other SSFA honours this year went to St Aidan's High (Wishaw), who beat Renfrew High 3-1 in the U16s, and Oban High, who beat Peterhead Academy by the same score in the U15s. The U13 and U14 events are at the semi-final stage. Craigmount meet St Machar's in Dundee next Friday in one U13 semi.

The Glasgow association's centenary is in October. Scottish schools football is in good heart for another 100 years.