I have been down this road as well just recently I was asking about 1800's this is the reply I received from the Manx Museum.
Hope this helps...Brian..... www.kneen.com
Most of the school records we hold are Log Books for individual schools, although there are a very few registers. I can see no dates earlier than the 1860s.
Have you looked at An Island that led: the history of Manx Education, vols 1 & 2, by Hinton Bird? It can be useful for biographical information on teachers. It may be available through inter-library loans at your local library.
Manx National Heritage
Douglas, Isle of Man, IM4 3LY
Tel: +44(0)1624 648000
Fax: +44(0)1624 648001