Hi Alex,
Foundation is indeed a sub-category of Students Professionals category, but your menu is a single menu item which has no sub-menu items. The current menu item, or current parent/ancestor item active status are determined by the structure of currently selected menu item versus the currently loaded page/category. And right now, there is no menu hierarchy to compare them, thus it doesn’t have active status since Wordpress can’t determine if the current page is a sub-menu item of a specific parent menu item.
The only workaround for that is custom development that we can’t provide here in the forum. But right now, Wordpress doesn’t apply active class status (parent-child, and there is no child menu item), so any CSS will not work either.
Thanks!