Olle Nygren would run 'Training Schools' at King's Lynn during the seventies and eighties but it was more for the benefit for people like me who wanted just to have a go...although I know that he would run schools for foreign riders which were somewhat more official.
As I mentioned earlier 'Speedy' Pete Jarman ran winter schools during the winter of 75/76 at Cowley and Len Silver's schools at Hackney were well received (remember John Noakes and Peter Purvis of 'Blue Peter' fame having a go!) and Garry Middleton used to run schools (Michael Lee attended one such session I remember).
Mildenhall, King's Lynn, Rye House and Eastbourne ran schools throughout the early seventies and were rewarded with a flow of riders...some 'schools' however were just an opportunity to test/run a bike with very little instruction.