Ok. I think this is the issue.
When not logged into the site (this is the case for students whilst in school), there are still sections of the site that they are able to navigate to, without being pestered for credentials.
The way the site has been setup, is so that when not logged in, the front page displays all posts that have posted to either; any of the 7 year groups, or the ‘Everyone’ categories. I think what is happening is that, say 1 out of the 5 posts (I say 5 as this is the value within the ‘dashboard – settings – reading – blog pages show at most [ ] posts’), has been directed to the category groups mentioned above, but the the remaining 4 posts have been directed to a staff only category, only the single post directed towards a student category would show! As there is only 1 student directed post out of the 5 for that page, it only displays 1 post on the page. If there were for instance, 2 out of 5 posts for a page that had been directed towards students, it would show only those 2 for that page, and NOTHING else on the page. If this is the case, and I think it is, it involves navigating through the different, and numerous pages, to track down the other posts. Is there any code that I could implement, so that WordPress continues to scour which are student category directed posts, but consolidates them all, and displays consecutively, using all the page space available (so that say, 10 posts are spread across 2 pages as opposed to many). Any ideas? Apologies for the mind blowing explanation!