Submenus and different menus for sub pages

Hi all. I'm trying to set up a site so that a different top menu appears for each submenu. For example, alexandracollege.eu/150years.

This is a mocukup. I would like this top menu to appear for this section.

However, I would like a different menu to appear on top when I click on, for example, Senior School, on the left.

What I'm thinking is that I can have different installs of WP for each area, e.g.:
alexandracollege.eu/150years
alexandracollege.eu/senior_school

but this seems messy. Is there a better way? Also, is there a way I can force the top menu into the centre column so that it appears above the main content?

Thanks all and hope this makes sense!!