Hi, welcome to Wiki.
I wrote a post a while ago about the school, which you can read Prenton Secondary School for Boys
. It covers the History
of the school both before and after the girls department was split off into a new school on the Bedford Road site. It covers a little of the period you are interested in.
The Girls school has a selection of posts in its own right on this site, but most refer to the 'new' school only. Check out the 'Schools' section on here.