The actual date the school opened will most likely be held in the archives of the Woodhorn Museum but I haven't checked them out so this posting is a guess at the date the school opened, based on the information currently available on the www :-
The modern grammar school concept dates back to the Education Act 1944. This made secondary education after the age of 14 free.
At the same time secondary education was reorganised into two basic types:
grammar schools, which focused on academic studies, with the assumption that many of their pupils would go on to higher education
secondary modern schools, which were intended for children who would be going into trades.