CSS current states

Okay,
I’ll try not to confuse anyone, but its a slightly confusing matter.
Please see the website for reference.
https://www.kindergarten.edu.hk/english_2011/wordpress/?page_id=151

Now, as you can see its a multi-level menu, with 2 sub-menus.
The problem I have is setting the current state for the li that open the sub-menus. As you can see the “about us” button is black, when I try to have it in white, it turns the whole sub-menu white.

Same goes to the “Our schools” – if I click it, due to the current state the whole sub-menu becomes white, until I select an item in the submenu!
What can I do! Please help!