Hi LawrenceL, the teacher you are referring to was Colin Finbow.
He taught English and ran the Film Society at FHS. I think he was also involved in the Children's Film Foundation. Many films were made at the school including one I was involved in called Crying River made in 1974/75 at Aberllefenni. I have often wondered what became of the films and if the school still has them somewhere. Films were also shown in the evenings and provided you had your parents permission we enjoyed showings of A Clockwork Orange & Willard (about Rats!) amazing really.