The navigation menus on a mobile phone do not extend to as many pages as on a PC. You get to them from other pages.
They may have a button at the bottom, as at the bottom of this page, that takes you to the most likely previous page(s). It may be handy in navigating the website.
Most off-menu pages do not appear on PC menus either.
Alternatively, see shortcuts in 
menu at top right of screen.
Special educational needs
Mobile guide