St. Patrick’s Schools obviously do not follow the consistency theory.
When I went to one of the St Patrick’s schools, I was told that when there were four things, then the object would be in the plural – so it would be ‘four schools’ and not ‘four school’.
They also explained the apostrophe as being used to replace the word ‘of’. To understand whether an apostrophe should be used, we were encouraged to rewrite the sentence using ‘of’ - just like ‘Campus of Schools of St Patrick’ or even ‘School of Boys of St. Patrick’.
It appears that the means of education has changed in the intervening years.