AFTER 65 years of racing, the Mudhook Yacht Club's annual Schools and Cadets Week is an essential institution in Clyde sailing. As generations of sailing families have packed off their youngsters each year since 1933 to do battle on the Clyde, this series has maintained its immense popularity, a magical ethos and has long since become the essential rite of passage in the early years of any sail racing career.

Set up by the club to offer young sailors between the ages of 13 and 18 the opportunity to race equally matched one-design keel boats, which would not be available elsewhere in the UK, the series remains just as unique now on the British sailing calendar. As a consequence it continues to be over-subscribed each and every year.

The successful recipe is equal measures of ''Swallows and Amazons'' serious racing regatta, and early steps on the big-boat racing learning curve. Add water and a demanding social programme with parental control pushed subtly to the background, and few who have participated in this series will recount their cherished schools week memories without a smile.

While many skippers and crews have gone on from schools week success, or failure, to greater things in sailing, so the tiny details etched into the memory banks about schools week long outlast those from many more exotic regattas.

Initially the week was open only to schools and universities with the younger school pupils racing Dragons and university students contesting the Olympic class of the day.

It is now raced in a fleet of 14 Piper dayboats, which were designed by David Boyd for the International Regatta of 1973. The boats are loaned each year by their owners, and while each has a 'caretaker' aboard they are not allowed to have any input to the race strategies other than to avoid collisions.

Racing takes the form of a continuous round-robin in a fleet of 10 boats, with all change-overs afloat unless the weather dictates otherwise. Crucially there are no discards allowed so all scores are included in the aggregate. With the possibility of disqualification if judged to be on the wrong side of a rule infringement, protests can prove costly and a full understanding of the racing rules is therefore essential.

At stake are the Clark Cup, for the overall winner, the Young Cup, and the Christie Cup. While once the Young Cup was for universities, if it is a club team which lifts the Clark Cup then it goes to the best school crew. The top all-girl crew win the Christie Cup.

To date Kelvinside Academy are the only school to have won the Clark Cup five times (1933, 34, 35, 54, 76), while Northern Ireland's Bangor Grammar School (1958, 64, 77, 79), and Edinburgh Academy (1948, 50, 67, 84) have both won four times.

The roll of honour on the principal trophies naturally records the early victories of Scotland's future sailing stars. The Budgen brothers, Andy and Ian, second in the world in the 49er class at the moment, won the Clark Cup three times between them for Gourock Academy (1987, 88, 89).

Three-times Scottish Series-winning helm Jim McIlwraith won in 1972 for Rothesay

Academy. In the 1950s George McGruer of the famous Clyde boatbuilding family won. His family owned the land on which many competitors camped and the boatyard was also the venue for the series in the 1970s. Cove Sailing Club's Murray Caldwell is the most recent helm with three wins to his credit.

Scottish Olympic gold medallist Mike McIntyre, in contrast, is one competitor for whom schools week success proved illusive.

''It is actually a very difficult series to win because the standard is so high and 'everyone who is anyone' does it,'' comments Caldwell. ''Because it's a no-discard series, it really teaches you to be consistent.''

The club's Admiral Ronnie Sharp emphasises that they have no plans to enlarge the series in the near future. ''We don't want it all to get too much and we aim to try to get the balance right between teams who are just cutting their teeth and those who are already experienced.''

Entries are limited to 30 teams currently and that means officials have to ballot prospective entries and care is taken also to ensure an equal balance is maintained between fee-paying, state sector, and club teams from all over the UK and Ireland.

The newest asset the regatta boasts is the regular attendance of the Royal Yachting Association's world renowned senior national racing coach, Jim Saltonstall, MBE, who has launched almost all of Britain's recent Olympic medallists on their early careers.

Armed with video footage, Saltonstall feeds back to the youngsters with his assessment of their daily gaffes and triumphs.

In the interests of evening out the differences between the various boats, Mudhook members recently contributed to the purchase of 15 identical new full sets of sails for all of the boats and these sails are used only at Schools and Cadets Week.

The youngsters generally camp in the gardens around the Gareloch area of local club members or sleep aboard the numerous yachts belonging to competitors' parents.

The Mudhook Yacht Club, by virtue of the fact it was set up to have ''40 members and one forbye'' may be small and exclusive, but it has gained a cherished reputation for promoting and aiding excellence in regatta and rules management. The club celebrates its 125th anniversary this year and as well as having among its members Prince Philip and the Princess Royal, has three international sailing judges, eight national judges, and seven international race officers.

Racing at Schools and Cadets Week is sponsored by the Crown Estates Commission and starts this Monday at Gullybridge on the Gareloch. Dunoon Grammar School achieved a notable double last year and will be setting out to defend both the Clark Cup and the Christie Cup. Significantly the series arrives near the end of the holiday period and all the competitors having toured the summer's major regattas should be at their peak.

Among the favourites this year are Young Cup winner Peter Austin of Cove Sailing Club who has just placed second at Loch Long Week as crew, Tarbert Loch Fyne Sailing Club's Ruaraidh Scott who has been competing at the highest level in the 1720 Class at Ford Week in Cork, Ireland.

Few who have participated in this series will recount their cherished schools week without a smile